Actually thats not completely true, there are several modes in each person. For example third person 'limited'; where the description is 'anchored' around a certain character and thus so is the knowledge - the narrator knows all and tells all about a certain character but is as in the dark about everything else as the main character .
Then you have third person 'omniscient' which is all knowing and thus far more authoritative in tone. And also third person 'objective' where the author knows nothing but what is currently being seen or heard (as opposed to thought and felt) rather like a video camera.
First person is similarly split in to 'protagonist' and 'witness', where you have a character within the story narrating - rather than direct emotion from the characters involved we are getting a narration not too dissimilar form third person limited. Whereas protagonist is the traditional "I did this" type of speech.
Second person is where you write 'you did this, you walked there, you spanked that elephant', and is often an immense flop [though it can be useful in depictions of insanity]. Second person can also often present difficulties in that it requires a certain amount of 'co-operation' between reader and protagonist. Here's an excerpt from Jack Hodgins
Passion of Narrative to demonstrate:
"I went along with you when you told me I entered the rooom. I didn't mind when you told me I accepted the drink. But when you told me that I put a hand on your thigh, I went 'No way, pal. I'm outta this story right now!''