Google is so big and so wide in its scope that it is hard to know where to place this category so that it is easy for users to find so I am creating a whole category for it. Here since I plan to cover topics that are relevant to site owners, developers, and also (site) advertisers.
If you are using multiple Google products (e.g. Gmail, AdSense, Analytics, SketchUp, etc.), it more than likely that you can log into all of those sub-Google accounts via one Main Account login.
The very first thing that people seem to ask and have confusion about is "What is the difference between AdSense and AdWords?"