Re-Mortgage confuses me?

If you intend to stay in your house,why re-mortgage? Is it to release the equity to improve it or just to have some spending money? What you are talking about,is that if you wanted to move to another house,you can use the equity as a deposit. In a years time,and your fixed rate stops,you negotiate a new mortgage at a better rate and any equity gained cuts the % amount you borrow.Hope this makes it clearer for you.