In third person limited the narrator only knows the thoughts and feelings of <em>one character</em>. All characters are described using pronouns, such as 'they', 'he', and 'she'.
The third-person omniscient point of view is a method of storytelling in which the narrator knows the thoughts and feelings of <em>all </em>of the characters in the story.
Mainly using i and me in a sentence identifies that the story is in third person.
EDIT: sorry wasn't thinking straight, so third person is you or the narrator seeing/feeling/visualizing the character that is in play. just imagine as if you are stalking that person like a ghost! and you see everything they do and feel, emotionally of course. its just like watching a movie you're the third person.