DeclareTrigger rules to cause an activity to run when instances of a specific class are created, updated, or deleted in the database. This implements a form of forward chaining.
A database trigger is procedural code that is automatically executed in response to certain events on a particular table or view in a database. The trigger is mostly used for maintaining the integrity of the information on the database.
Declare Trigger is specific to PRPC whenever class gets updated, deleted etc it will get fired.