The && means "and then, if that worked". Each command only runs if the one before it succeeded.

Read mkdir trip && cd trip && pwd out loud: make a folder called trip, and then step into it, and then say where I am. If the mkdir had failed (say the folder already existed) the cd would never have run, which is exactly what you want: there is no sense walking into a folder that was not made.

A chain like this either gets all the way to the end or stops at the first problem. It is how one line can safely do the work of three.