Tremendous=Very good. For example: "I just got promoted at work. Isn't that tremendous?" Enormous=Very big. For example: "Look at that big truck. It's enormous." Both of these words are a little formal, or at least, a little old-fashioned. For very good you can say great/awesome/wonderful. For very big you can say huge/massive/gigantic.

I agree with Janet. Example: I heard a tremendous explosion.

Or I have been experienced a tremendous thing ?

@Janet:for this word .can I say : I have got promotion.It's so tremendous ?

I agree "tremendous" can mean very good. But I also use it and hear it used for very big, similar to "enormous."