Move_group_interface_tutorial: orientation vs. position

Hi! I am learning how to plan my robot arm with moveit following pr2_tutorials: http://docs.ros.org/indigo/api/pr2_moveit_tutorials/html/planning/src/doc/move_group_interface_tutorial.html What i dont understand is: 1 - what it's the diference between orientation and position? 2 - I try to move my end effector with only position x,y,z and it didnt work, why? 3 - Right now i always plan with joint space goal and read the positions to then plan with pose goal or path. Is this the way, or it is a better method to plan with coordinates? Can you help me clarify my doubts? Thanks