At the January, 2011 Maple Ridge Workshop, Master Chen talked about the levels of skill in push hands.
He explained that level one is structure, level two is space and level three is timing.
When we can maintain good structure, we can use that structure to create space between ourselves and our opponent ( a safe zone). If we are at level two, we have learned how to physically take away our opponents space. When we can do this, we are able to put ourselves into a position to accomplish an action like a push.
If we are at the third level, we understand how to use timing to put ourselves into a good position. Using timing is a much more efficient way to take up space.