It depends on what's going on; you mention an alias, and then you mention a redirect, but these are not the same thing.
The following says, when somebody accesses
http://myurl/image, serve up the contents of
/www/image. There is no redirect involved here. If a user submits POST data, it will be submitted to whatever path is specified.
Alias /image /www/image
On the other hand,
Redirect (which, confusingly, also lives in
mod_alias) will cause the user's browser to change to another page; using the same example as above:
Redirect /image http://myurl/www/image
So when your user accesses
http://myurl/image, your server will send back a message saying, "This page has been moved to
http://myurl/www/image", and your browser will resubmit the request to the new URL.
Keep in mind that you can have both an
Alias and a
Redirect clause on the same path, and the
Redirect will take precedence--keep that in mind when looking over your rules. If you really want to see what's going on, open up a terminal and try:
curl -I http://myurl.com/image
If you see
HTTP/1.1 301 (or
302) or similar, you are being redirected, and the
Location field will reveal the new location. Hope this helps!