As previously mentioned, the method Apache uses to handle multiple simultaneous connections is to manage a "server pool" of processes where incoming requests are given to idle processes in that pool. The master process runs as root, binds to port 80, and then forks children for the server pool; these child processes revoke all root privileges and run as an unprivileged user and group (typically "nobody" or "www"). If there are too few idle children, the master process creates more; if there are too many, it kills some off. Apache 2.0 can use "threads" (multiple threads of execution in a single process) in addition to individual processes to manage requests, although this is typically not necessary except for extremely high-volume or high-performance web servers; the one-request-per-process model typically performs adequately and is simple and robust.
Apache is configured via a file httpd.conf which contains configuration directives usally followed by arguments. It can also use SGML-style (SGML is the meta-language of HTML) syntax to scope other configuration directives.
Older versions of Apache, and NCSA httpd, used additional config files access.conf for access control directives and srm.conf for directives relating to content handling, namespace aliasing, and some other things. These directives can now be included in httpd.conf and use of access.conf and srm.conf is deprecated.
Some per-directory configuration can be performed by placing configuration directives in .htaccess files in content directories; the directives apply to the directory the .htaccess file is in and all subdirectories of it. The web server administrator can limit which directives will be honored in .htaccess files with AllowOverride directives in httpd.conf scoped to the directories they should apply to.
An operation manual including detailed information on Apache configuration is in the docs/manual subdirectory of the distribution, which is also installed in your web server's document root by default. We have a local mirror of the documentation you can also use.