What is "configuration"

The configuration is used to customize the behavior of a program. It is commonly done using static configuration files that can be composed in any common text editor, but some applications provide tools (sometimes even with graphical interfaces) to create, modify and check the syntax of your configuration files.

Some programs only read their configuration files on startup. Others periodically check the configuration files for changes. Users can instruct some programs to reread the configuration files and apply the changes to the current process, or even to read arbitrary files as a configuration file.