My favorite description of UX: You go to open a door with a "C" curved handle. Do you push or pull the door to get it to open?
This is a standard usability issue, because many times the design gives you wrong usability signals. You have to try both ways before getting the door open. My work is researching and designing to make sure that isn't an issue, making things easy to use. This example was written about by Don Norman in his book "The Design of Everyday Things".