From the cloud code tutorial:
Using Cloud Code also allows you to create your own custom Events to pass data to and from the servers.
Events require specifying shortcodes and event attributes, requests don't.
What is the fundametal difference between event and requests/responses?
When to use which i.e. I'm creating a service for managing CRUD for a MongoDB collection.
Should each service method be exposed as an event?
Requests/Responses is for internal gamesparks events like DeviceAuthentification. They are hehre so you can modify their behaviour before (request) or after (response) they are called