Apache has two ways to serve one page when you were asked for another: Rewrite* rules via mod_rewrite (e.g. RewriteRule, RewriteCond), and Redirect* rules via mod_alias (e.g. Redirect and RedirectMatch).
What are the differences?
mod_rewrite is generally considered the more powerful, and more complex, solution. It offers the RewriteCond directive, which lets you only run a Rewrite rule if certain conditions are met.mod_alias is simpler, and lets you match on a simple string or on a regular expression, but does not allow you to put conditions in (other than those defined by the regexp)