Delimiter and Trigger Inquiry

May I know what does the following trigger does, and I am questioned on how to prevent this.

DELIMITER ??
CREATE TRIGGER before_results_update
BEFORE UPDATE ON Student_Results
FOR EACH ROW BEGIN
INSERT INTO Result_Changes
SET ACTION = 'update',
ResultID = OLD.ID,
Result = OLD.Result,
User = USER(),
ChangedOn = NOW();
END ??
DELIMITER ;

Thank you

*Ruing Kali-Linux on Oracle. Using MySQL