What a reformer is
How a Pilates reformer works
A reformer is a sliding carriage on a frame, pulled back by springs of different tensions, with a footbar, shoulder blocks and straps. You push or pull the carriage against the springs lying, sitting, kneeling or standing, which loads the whole body through controlled range of motion with low impact. It is the apparatus most Pilates studios are built around, and a home reformer gives the same exercises without class fees.
Oak frames are the traditional studio build: heavier and more stable than aluminum, quieter, and they look like furniture in a room.