The default scope for a variable is the enclosing container. If outside a script, or other container then the scope is Global. To specify a scope, it is prefixed to the variable name $scope:varname like so:
$foo = "Global Scope"
function myFunc {
$foo = "Function (local) scope"
Write-Host $global:foo
Write-Host $local:foo
Write-Host $foo
}
myFunc
Write-Host $local:foo
Write-Host $foo
Output:
Global Scope
Function (local) scope
Function (local) scope
Global Scope
Global Scope