<database> An action causing the automatic invocation of a procedure, for instance to preserve referential integrity. A triggers goes into effect when a user attempts to modify data with an insert, delete, or update command. A trigger can instruct the system to take any number of actions when a specified change is attempted. By preventing incorrect, unauthorized, or inconsistent changes to data, triggers help maintain the integrity of the database.
[Sybase SQL Server Release 10.0 Transact-SQL User's Guide].