How to reset Terminal to initial settings?

Hi all,

I lately have been trying to learn programming through online sources (particularly YouTube). I managed to fiddle around with the terminal application successfully but I am afraid I have done some damage. Since my knowledge of computers is so small, I don't know what I have done. I just know that it is not behaving the way tutorials expect it to.

I would like to reset the Terminal to how it was without me touching it. Is there away to delete my progress and start fresh?

Thanks.