The source command is a built-in command in Unix-based operating systems like Linux and macOS that is used to read and execute commands from a file in the current shell session.
When you run the source command followed by the name of a shell script file, it reads and executes the commands in that file as if they were entered directly on the command line. This is useful for setting environment variables, defining functions, or running scripts that modify the current shell environment.
The . (dot) command is an alias for the source command in most shells.
Both source and . can be used interchangeably in most cases.