Apache HTTP Server can either be downloaded and installed or be installed through a package repository if the target system (Linux/Unix) has one. If available installation through the package repository is the preferred way of installation.
For the latest and more detailed information check the 'Compiling and Installing' chapter in the documentation of the latest version of Apache HTTP Server.
On most operating systems, the Apache HTTP Server package can be installed from a package repository. For example the '/usr/ports/' repository for FreeBSD and the 'apt-get' package system for Ubuntu and Debian Linux distributions. This will download AND install Apache HTTP Server on the default location depending on your OS with default modules and configuration.
Always use the operation system package repository instead of downloading and compiling from source if there is an package repository available.
Apache HTTP Server downloads can be accessed through the following URL: http://httpd.apache.org/download.cgi
Installation on Windows operating systems
Read the important notes mentioned on the download page for Win32 distributions