Mastering PowerShell scripting often involves comparing things. This includes learning how to branch using if/then/else, how to build loops with while and foreach, etc. For example, consider this code:
 
if ($x –eq 1) {
 write-host "x is 1"
} else {
 write-host "no it isn't"
}

 So how, exactly, do if and else work? Help is available for all these things, but in some cases it’s hard to track down. PowerShell’s help contains a lot of topics in the form of about_something. For example, there is an about_if, which talks about both the if and else statements. You can see all of them by typing “help *about*”. The other thing to note in the statement above is the use of “-eq”. This is a so-called comparison operator, and mastering these is very important. Type “help about_comparison_operators” to learn all about these.

Here are some common comparison operators:
 
Operator
-eq                           Equal To
-gt                           Greater Than
-match                    Matches a string using regular expressions
-ne                          Not Equal To
-contains                 Containment operator includes
-not                          Containment operator does NOT includes
-lt                             Less Than