They hardly need an introduction as most people have heard of Google and even use Google as a verb! However there is some information that is worth highlighting and some useful links, so here goes....
So yes, this is the source of everything, however check out Google – My Activity for a summary of all your activity. It can be quite interesting/frightening. If you have an Android device then the Google Account you use on your phone/tablet will also show up at Timeline which shows you where you have been!
We all know security is always important, so check out make sure you visit Security Check-up, which is worth doing regularly.