Here is the video version, if you prefer it:
Let’s talk about how you can use auto-completion in the shell. When typing a filename, press Tab on your keyboard.
Let’s say I have a file named longFileName.txt. I can just type in long, press Tab and the filename will be filled for me automatically. This does not hold if I have two or more files starting with long. There must be only 1 file with that prefix in its filename (any ambiguity must be cleared) for auto-completion to work.
Hope you learned something useful!