A ".conf" file is a configuration file used by various software applications and systems to define settings and parameters. These files typically contain plain text and are easy to edit, allowing users to customize how a program operates. Common applications that use ".conf" files include web servers like Apache and database systems like MySQL. The structure of a ".conf" file usually consists of key-value pairs, where each line specifies a particular setting. For example, a line might define the port number a server listens on. Proper formatting is essential, as errors can lead to application failures or unexpected behavior.