How and when would I use tweening?

I am new to scripting and I am trying to make a model (train thing) in workspace to move smoothly along the top of a part (tracks) and then stop and specific points (train stations) for a few seconds. I am not sure but I have heard something like this needs something called "tweening". I have went through six tutorials already and none of them worked (they were probably outdated).

If someone could show me how to do this I would be most happy.

Thanks in advance!

PrismaticFruits