Consider the Logo
The Azure Functions logo is a lightning bolt.
This is how lightning works in the real world according to this fourth grade science text.
Much like the real world, Azure Functions can be described as an environment. We call this the Azure Functions Runtime.
You can think of the system that creates lightning as a function of the environment.
The function happens in the environment when the right conditions are met causing an event that triggers the function (such as a file being uploaded to storage).
A binding is what provides the information from the triggered event to a function instance. (ok, this one is a bit of a stretchy analogy).
Execution is when it all comes together and the function runs.