The Re-write function replaces the Redirect Option found in the Web Service site section of the Console.
The Web Service - Site - Redirect option in the Administration GUI allowed you to define redirect rules based on the URL and URI. The requests that came to the server based on some string criteria were redirected to other pages. This option has been renamed to Rewrite and currently supports the old functionality for backward compatibility and a new mod_rewrite regex replace mechanism.
Non-RegEx (old way) does always redirect and the user can see the change in browser address bar. RegEx way rewrites the URL internally so for the user the URL appears to be the one shown in address bar.
Alias option has been renamed to Directory Aliases and is strictly for virtual directories. This functionality remains the same as used to be but is a bit simplified, updated and working in the end. You can have a relative alias (pointing to the current web site repository, /mail/ -> webmail/) or absolute pointing to any directory or disk on your computer - /data/ -> /www/mydata/. Subdirectories are also supported, there's a new no match strings function.
Changes summarized: