As part of your business workflows, records are regularly inserted, updated, and deleted. To customize the system behavior, you can hook into some of the record operations that are most often used. For example, you can fill additional fields on the record, perform additional data validation, or insert additional data into related tables. Several events that are available on the table let you achieve those customizations through extensions. Your code can subscribe to these events, and can insert your logic before or after the event is run.
For a list of the events that you can subscribe to, see the "Table extensions" section in Customize with extensions and overlayering.