An adjustable-rate mortgage is a mortgage loan with an interest rate that periodically adjusts according to various indices. An initial interest rate remains fixed for a set period of time, after which the rate is reset and monthly payments are recalculated.
ARM rates are often the lowest available – especially in a housing market like this one! You can select the number of years for the fixed-rate portion of your loan, and after that period, if the market is doing well, your interest rate might even drop! And since initial rates are so low, an ARM may help you get into a larger house than you could otherwise afford.