Authentication is any process by which you verify that
someone is who they claim they are. Authorization is any
process by which someone is allowed to be where they want to
go, or to have information that they want to have.
The CGI (Common Gateway Interface) defines a way for a web
server to interact with external content-generating programs,
which are often referred to as CGI programs or CGI scripts. It
is the simplest, and most common, way to put dynamic content on
your web site. This document will be an introduction to setting
up CGI on your Apache web server, and getting started writing
.htaccess files provide a way to make configuration
changes on a per-directory basis. A file, containing one or more
configuration directives, is placed in a particular document directory,
and the directives apply to that directory, and all subdirectories thereof.
SSI (Server Side Includes) are directives that are placed in
HTML pages, and evaluated on the server while the pages are
being served. They let you add dynamically generated content to
an existing HTML page, without having to serve the entire page
via a CGI program, or other dynamic technology.
On systems with multiple users, each user can be permitted to have a
web site in their home directory using the UserDir directive. Visitors
to a URL http://example.com/~username/ will get content
out of the home directory of the user "username", out of
the subdirectory specified by the UserDir directive.