Difference between Synchronous and Asynchronous Events

The primary differences between Sync & Async event handlers are :

1) Synch Eve Handlers will work before the event is completed while AEH will fire after the event is completed.
2) SEH are mostly used to stop the event from completion in order to validate few things. It means you can cancel the event using SEH while it is not possible to cancel the event from AEH.
3) SEH methods has their method names ending with -ing while AEH method names will end with -ed. e.g. ItemAdding, ItemUpdating are SEH while ItemAdded, ItemUpdated are AEH methods.
4) SEH can be used to Add/Modify the values of list fields while using AEH its not possible as it fires after the completion of event.