Looking at the subject there are lot of blogs available but I am writing this based on one of the request from my colleague.
Everybody aware of that whenever you developed an app it need to be extensible and if anybody would like to add or modify any field or additional routing we need to have events which can extend the base functionality.
Step 1 :- Simple Quick action to add event in Business Central
Next step will be we can subscribe the event and add you own code.
It is so simple to add custom event in AL and allow other to extend your functionality.