Bash has several commands that comes with the shell (i.e built inside the bash shell).
When you execute a built-in command, bash shell executes it immediately, without invoking any other program.
Bash shell built-in commands are faster than external commands, because external commands usually fork a process to execute it.
In this article let us review some useful bash shell builtins with examples.
Full article here:
15 Useful Bash Shell Built-in Commands (With Examples) (The Geek Stuff)