The AddEncoding command associates the given file names or extensions (for the services that don't automatically include them, like ftp:// or file:///) with the specified content encoding types.
The first two optional parameters specify comparison type. The default comparison type is String and Case (case insensitive string pattern match with ? and * wildcards meaning one character and any number of characters correspondingly).
The pattern parameter can be repeated multiple
times, to associate a content encoding type with multiple
extensions in a single command.