A residential mortgage is simply a loan taken out against a property that you and / or your immediate family intent to live in as your main residence. Residential mortgages usually require a minimum of 5% deposit (although some lenders will require no deposit, but will have much stricter criteria and less preferential rates). You will also have to meet certain income requirements based on the size of the loan that you are looking for and ensure that you meet the lenders other general criteria.
Most residential mortgages are on a Capital and Interest (or Full Repayment) basis, meaning that, at the end of the mortgage term you will have fully repaid you mortgage and own the property outright.