When standing in front of the machine, facing the machine, a positive X will move the tool to the right, or the table to the left. A positive Y move will move the tool away from you, or the table towards you. A positive Z move will move the tool up, or the table down. The home position can be wherever you choose to put it - at any corner, or even in the middle of the travels. It's completely arbitrary.
Regards,
Ray L.