That said, there's a difference between understanding what privilege you are granting and understanding the implications of that grant.
For instance, Google help pages [0] just talk about "Full account access" and "View your basic profile information." What about apps that can view your calendar? That's in between. What information do those apps actually see? What can somebody do with the information that I might not like? These are hard questions to answer with the information Google gives you.
Grant an application permission because it asked to in order to fulfill a request to handle one particular thing about one particular email. Instead, grant access to your entire email account, not get notified of which emails the application accessed, and get upset because the application exceeded what you desired to grant.
For instance, Google help pages [0] just talk about "Full account access" and "View your basic profile information." What about apps that can view your calendar? That's in between. What information do those apps actually see? What can somebody do with the information that I might not like? These are hard questions to answer with the information Google gives you.
[0] https://support.google.com/accounts/answer/3466521?hl=en