A residential mortgage is given to a borrower to finance the purchase of a residential property. It is intended to help a borrower finance the portion of the purchase amount that down payment does not cover. 

Fixed rate mortgage

Requires the borrower to pay the same amount during the whole term of the loan at an interest rate that does not change for the remainder of the term.
A fixed rate mortgage is great for people looking for consistent mortgage payments that will not change in the event that national and posted interest rates rise.

variable rate mortgage

Does not have a set repayment amount and fluctuates based on the national and posted interest rates. The initial interest rate offered by these mortgages is lower than fixed rates because of their potential to be unpredictable.
Variable mortgage rates can end up costing you more if national and posted interest rates start to rise.