When you "see" one of your friends flirting with the opposite sex, and sometimes the same sex.
Some of the times he/she may not even be flirting but in the situation you want to make shit awkward you may still "see" them.
(Person A walks up to person B and person C and sees them talking"
Person A: I see you!
Person B: Damn, he caught me...
Person C: Why does he see us?