Interest-Only Mortgage

What Does Interest-Only Mortgage Mean?
A type of mortgage in which the mortgagor is only required to pay off the interest that arises from the principal that is borrowed. Because only the interest is being paid off, the interest payments remain fairly constant throughout the term of the mortgage. However, interest-only mortgages do not last indefinitely, meaning that the mortgagor will need to pay off the principal of the loan eventually. 

Investopedia explains Interest-Only Mortgage
Interest-only mortgages can be useful for first-time home buyers because it allows young people to defer large payments until their incomes grow.

At the end of the interest-only mortgage term, the borrower has a couple of options. He or she can either renew the interest-only mortgage or repay it through standard means, such as entering into a normal mortgage and liquidating investments.