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So of course the first question becomes, what is a variable in PowerShell?

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A variable is really nothing more than a container,

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and don't confuse containers with Docker containers.

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It's just a bucket or a place to hold something that we get in PowerShell.

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The variable itself is empty.

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It's nothing.

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It's meaningless.

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It doesn't have anything to do with anything until we put something in it.

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And variables are what make PowerShell reusable and easy to use,

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so that's why it's important to learn how variables work.

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When you start PowerShell,

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you actually get a lot of built‑in and automatic or predefined variables.

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Obviously, you can also define your own variables,

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and with variables more than likely you can change the values of them.

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And that speaks to the name of this thing: it's a variable,

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so the value is variable.

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It varies.

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It can be foo one minute and then bar the next.

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In your PowerShell session, variables are persistent,

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but they're not persistent across PowerShell sessions.

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To create a variable, really all you need to do is assign a value.

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And there I'm using the equals sign, so I'm going to create a variable,

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and the name of the variable is a, and I'm giving it a value of 1.

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The dollar sign is only used when we want to

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reference that variable in PowerShell.

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So if I type $a, I can see that the value is 1.

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PowerShell shows me the value of the variable.

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If I want to change the value of a, I can just assign a new value of 2 to $a,

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or the variable a.

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So assigning it, very simple.

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And again,

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this will last for the duration of my PowerShell session or

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until I change the value of $a again because variables really

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are nothing more than placeholders, so you can create a variable,

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put something in it, and then use that variable.

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For example,

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I can run Get‑Vegetable and pipe it to

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Select‑Object and use the ‑First parameter.

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The ‑First parameter wants an integer saying how

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many objects do you want to select?

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Instead of me having to hard type 2, I'll just use the variable $a,

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and so the number 2, which is the value of a,

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gets plugged in and I get 2 objects that come back.

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So the variable is the placeholder.

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If I change the value of $a and rerun the command,

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then I'll get something different.

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For example, let's set $a equal to 5.

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Same variable, all I've done is just change the value that is inside it.

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Now I can run a command like Get‑Process.

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Same idea as Select‑Object ‑First $a.

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Whatever $a is, that's what I'll get.

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Now in this case I'm also going to do something else with the variable.

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I'm going to create a variable $b that will hold the contents of

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that Get‑Process Select‑Object expression.

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So I can use $b as a placeholder for that expression that created it.

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So instead of having to run Get‑Process, I can just reference $b.

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And then I can select the name properties of those objects.

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Now remember, $b only has the first five processes.

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The variable placeholder makes this really simple.

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In this case,

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you can use the placeholder $b for anything that you would want to do with it.

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So instead of having to run potentially a long‑running command,

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Get‑Process really isn't,

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but say I had some command that was going to run and take a long time to run,

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and I want to rework with that data, I don't want to rerun the

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command, save the results to a variable like $b,

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and now instead of selecting the name,

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all I say is give me the objects sorted by the working set property in

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descending order and then select some properties.

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So using $b makes that so much easier.

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I don't have to rerun Get‑Process or whatever the long‑running command is; I

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can just use the variable that is holding the results.

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As I said, this becomes very handy if you're running commands,

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say, like Get‑ADUser,

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where you may be returning 5,000 objects and that takes a long time to run,

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or Get‑EventLog or GetWinEvent, I should say,

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in PowerShell 7, that takes a long time to run.

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Saving to a variable makes your life a whole lot easier.

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Now there are also cmdlets that we can use to work with variables.

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Variable is the noun, so there's ways that we can get variables,

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set variables, create new ones, or remove them.

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Most of the time we're just going to be assigning

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values and changing the values.

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It's really that simple.

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Variables, when you create them, are generally independent.

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What I mean is,

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you can remove the variable without affecting the original source.

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And also, you can remove the original source without affecting the variable,

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depending on what commands that you are working with.

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Don't assume that the variable will update if the source updates.

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Sometimes it does; sometimes it doesn't.

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But you really need to test everything if you're using variables in this placeholder concept that I'm talking about.