In Linux and Unix-like operating systems, files and directories that start with a dot (.) are usually hidden from the user by default. These files and directories are known as dot-files or dot-directories.
Dot-files are usually used to store configuration information and settings for various programs and tools. For example, the .bashrc file in the home directory stores the configuration settings for the Bash shell, and the .ssh directory stores the user's SSH keys and configuration files.
Dot-files are not unique to Linux and Unix-like systems. They are also used in other operating systems, such as macOS, to store configuration information.
To view dot-files and dot-directories in a terminal, you can use the ls -a command, which will show all files, including hidden ones. To access a dot-file or dot-directory, you can simply prefix the name with a dot, like this: ./.bashrc.
It is important to be careful when modifying dot-files, as they can affect the behavior of the programs and tools that use them. It is a good idea to make a backup of a dot-file before modifying it, in case you need to revert the changes.