Install apache2-doc by entering the following commands in the terminal:
sudo apt update sudo apt install apache2-doc
Apache HTTP Server (on-site documentation)
The Apache HTTP Server Project's goal is to build a secure, efficient and extensible HTTP server as standards-compliant open source software. The result has long been the number one web server on the Internet. . This package provides the documentation for the Apache 2 HTTP server. The documentation is shipped in HTML format and can be accessed from a local running Apache HTTP server instance or by browsing the file system directly.