When you buy a home, the loan that you get will be the "first" mortgage. After you've built some equity, you may decide to tap into it by taking out a loan using the equity as collateral. This is called a home equity loan. This loan is generally talked about as the "second" mortgage and it's separate from the original, first mortgage. If you decide later to refinance, then any mortgages that you have on your home -- the first and second mortgages -- are paid off at that time. The outstanding balances are typically rolled into the new loan which then becomes a new first mortgage.