Contexto
Setting a timeout function
Setting a timeout function follows exactly the same principles with the interval, but this time the body function is not executed periodically until is cleared, but waits instead, for a given amount of time and executes itself only once.
In this case if we put the same function as before that prints 'hello world' message to the console, and 3000 milliseconds, a 'hello world' message will appear to the console after 3 seconds but only once!
It is mainly used for popping up windows, after 5 seconds for example, (giving first some time to the new user to get himself/herself used to the content).
Find out the setTimeout function documentation here