Flipping vs. rotating
Flipping means turning your mattress over to another side. The side you were sleeping on now faces the bed frame and a fresh side means turning it over, so the side you were sleeping on is now facing the bed frame.
Rotating means turning your mattress 180 degrees. That is, the end you placed your feet is now where you place your head.
The primary aim of flipping is to provide a fresh sleeping surface. Beds produced in recent years are not designed to have slept on both sides. You can rotate your mattress instead of flipping if only one side is comfortable enough for sleeping.
Rotating does not improve sleeping conditions as well as flipping, but it can still help stop early sagging and increase the lifespan of your bed [3]. It ensures your weight is distributed evenly across the bed.
Some mattresses are not made for rotating or flipping. For example, mattresses with a zoned design [4] should not be flipped or rotated regularly, because it reduces their durability.
To get the best out of some mattresses, you can flip and rotate them regularly.