A .cfg file is a plain text configuration file used primarily to store settings for a software application or a hardware device. It contains parameters that dictate how the program behaves, such as user preferences, system paths, display options, or connection details. Unlike executable files (.exe) which contain code to run, .cfg files are simple text documents containing key-value pairs or specific syntax instructions read by the associated program to initialize its environment.

Common practical examples include game settings files. For instance, many PC games use a settings.cfg file to store graphics quality, control mappings, and audio levels, allowing customization. In the realm of networking and IT infrastructure, devices like routers or firewalls often rely on .cfg files to store complex configuration settings, enabling administrators to back up, restore, or deploy standardized setups efficiently across multiple devices.

The key advantage of .cfg files is their human-readability and simplicity, enabling straightforward manual editing with basic text editors for customization. However, this accessibility can be a limitation: syntax errors introduced during manual edits can cause program failures, and managing numerous configurations can become cumbersome. While newer formats like XML, JSON, or YAML are increasingly popular for structured data, .cfg files remain widely used due to their simplicity and ease of implementation. Future trends might involve more automation tools to prevent manual errors but the fundamental concept persists.