Depending on what you are really trying to accomplish, you might find it useful to learn how arrays work. Consider the following example:
$array = @("Var0", "Var1", "Var2")
$index = 1
The first step creates an array with three elements, and stores it in a variable. Note the inclusion of the entry for zero, before the entry for 1.
The second step stores the value 1 in a variable.
The third step uses the variable with value 1 as a selector to choose the right element in the array. Note that if Index had been zero, it would have picked the first element of the array.
This is a very common technique in powershell, but it may or may not be relevant to your use case.