An Adjustable Rate Mortgage (ARM) is a type of mortgage where interest can change over time. There are two portions of an ARM:
ARMs usually have a promotional rate so the interest can seem lower than other mortgage options. Depending on your situation, it may make sense to refinance the adjustable rate mortgage into a fixed rate mortgage right before the promotional rate ends.
Similar to Fixed rate mortgages, borrowers can get a maximum of 10 Fannie/Freddie mortgages.