When creating a variable in the console (outside of functions or script blocks), the local scope is global. The global scope can be accessed from inside a function (child) because it is a parent scope:

Remove-Variable thisValue -ErrorAction SilentlyContinue 
$Local:thisValue = "Some value" 
"From Local: $local:thisValue"          # Accessible 
"From Global: $global:thisValue"        # Accessible 
 
function Test-ThisScope { 
    "From Local: $local:thisValue"      # Does not exist 
    "From Global: $global:thisValue"    # Accessible 
} 
 
Test-ThisScope 

When scopes are explicitly named as this, the source of a variable value can be reasonably clear. If the scope prefix is removed, PowerShell attempts to resolve the variable by searching the parent scopes, as follows:

Remove-Variable thisValue -ErrorAction SilentlyContinue 
# This is still "local" scope 
$thisValue = "Some value" 
 
function Test-ThisScope { 
    "From Local: $local:thisValue"      # Does not exist 
    "From Global: $global:thisValue"    # Accessible 
    "Without scope: $thisValue"         # Accessible 
} 
 
Test-ThisScope 

The thisValue variable was created in the global scope. As the function does not have a similarly named variable in its local scope, it walks up the scope hierarchy and picks out the variable from the parent scope.