Our socks, sleeves and tights were designed to provide true graduated compression, where the amount of compression decreases as the distance to the heart decreases.
In a sock for example, you'll find less compression at the top of the sock than at the toe. Or, in a pair of compression tights, there will be less compression around the waist than around the ankles. This forces the blood to move upward where there is more space.
So, while gravity is pulling blood down, compression is pushing blood up. That IS circulation. (Shoot. Did we spoil the magic?)