Understanding DELETE and DROP command

I a student of Computer Science. Recently I am trying to learn database. I found a link describing about the difference between DELETE and DROP command. I understand most of the difference between them with the most important one - DELETE removes only data where DROP removes the table/object too.

But I can not understand one difference - DELETE command fire a DML trigger where DROP doesn't fire any DML trigger. The link only state this fact without any explanation. Can someone explain it a bit, so that I can understand it more.

Thanks in advance.