1 Answer

If you are using the two words to describe someone, as in "Thomas was alert and oriented at all times." I would say:
Alert means that he is aware of his surroundings...sights, sounds.  He is "on guard" and listening for noises, looking for movement.  Think of a dog that is laying at your feet in the living room some evening.  There is a sound outside and the dog lifts its head, his ears picking up and he is attentive to hearing other noises.  THAT is "alert".
ORIENTED would mean "familiar with the surroundings".  He may enter an area he has never been before, but he surveys the area quickly and makes a mental map.  He knows where HE is in connection with the surroundings, and where other things are.  
A blind person becomes oriented with the layout of a room by touch....after surveying the room by touch, the blind person can maneuver without bumping into furniture because he has oriented (become familiar with the surroundings).
Hope this clarifies!