The Earth is approximately spherical in shape. The shape is termed Geoid. The picture above illustrates how we stand on the Earth. Some of us are actually standing upside down like bats hanging on a tree, relative to other people! It is the gravity that keeps us around the Earth. So, the idea of up and down is relative in the space or cosmos. It is relative to where we consider the ground.
(Photo Credit: www.dreamstime.com)