Apache Reference: mod_rewrite

mod_rewrite - Advanced URL Translation And Redirection
Since Apache 1.2, src/modules/standard/mod_rewrite.c
Ralf S. Engelschall (1996)

mod_rewrite is the Swiss Army Knife of URL manipulations. It provides virtually all of the functions one would ever need to manipulate URLs, and its functionality is highly generalized. Consequently, mod_rewrite can be used to solve all sorts of URL-based problems. The drawback is the high learning curve, because this module is based on a complex rule-based matching engine, which uses regular expressions for its patterns. Although the flexibility of mod_rewrite makes it a very complex tool, once you understand the basic idea you will master all existing and forthcoming URL-based problems in your webmaster's life.

Directives:

RewriteEngine    RewriteOptions
RewriteLog    RewriteLogLevel
RewriteLock    RewriteMap
RewriteBase    RewriteCond
RewriteRule