Apache HTTP server is an open source multiplatform software web server with the highest share of server installations around the world. The support is provided by a non-profit organization Apache Software Foundation, that also supports the OpenOffice package.
Apache has many features in the form of kernel expansion modules.
Examples of supported functions (modules): Programming languages on the server side (PHP, Python, Perl …). Authentication schema (mod_access, mod_auth, mod_digest, and mod_auth_digest). SSL, TLS (mod_ssl), proxy module (mod_proxy), URL rewriter also known as rewrite engine from mod_rewrite, configuration of log files (mod_log_config) and filtering (mod_include and mod_ext_filter). Compression (mod_gzip), Application Protection (mod_security). You can analyze the form of error messages and the created logs, for example, to know the amount of traffic, that passes your web server.