Apache is a freeware web server, a software that accepts HTTP requests from clients and sends HTTP responses. Apache is a cross-platform product, i.e. it can run on different operating systems Microsoft Windows, Linux, macOS, Solaris and others.
Apache has a modular architecture. The key element of a web server is the core, which is installed first. The user can then plug in any modules needed to accomplish any task.
The web server supports virtualization, i.e. several web sites can be supported on one IP address. For each host you can customize access rights and limit the use of computing power of the physical server.
Apache is written in C language, but there are modules that add to the Apache core support for other programming languages, such as PHP, Ruby, Perl and others. By installing additional modules, it is possible, using the SSL protocol, to configure the encryption of transmitted data between the client and the server.
With its intuitive interface, flexible modular structure, and built-in security mechanisms, Apache remains one of the most popular web servers.