The -or operator will return true if either the value on the left, or the value on the right, or both are true.

For example, each of the following returns true:

$true -or $true 
2 -gt 1 -or "something" -ne "nothing" 
1 -eq 1 -or 2 -eq 1 
(Test-Path C:Windows) -or (Test-Path D:Windows)