Returns a new string that is a substring of the specified string variable. The substring begins with the character at the specified index and extends to the end of the string, or to the specified ending index.
$[ScriptVariable]::substring(int beginIndex[, int endIndex])
The following example illustrates the syntax for the substring() string method:
$str = "AAABBBAAA"
$substr = $str::substring(3,6)
print($substr)
BBB