`.await` explanation

[alecandido]

In both sections 1.3. async/.await Primer and 3. async/.await there is no actual explanation of how .await is supposed to work.

The only attempt is in Why Pinning, in which it is written:

To understand why this is necessary, we need to remember how async/.await works.

Even though it is trying to recall something that has never been explained before...

The funny bit is that the async book is also the reference mentioned by the std docs about the keywords:
https://doc.rust-lang.org/std/keyword.await.html
While a more proper reference would have been The Reference: https://doc.rust-lang.org/reference/expressions/await-expr.html