How does the LBW law work in cricket?

Question

LBW is a term in cricket and I want to know that how does the LBW law work in cricket?

Answer 1

1) P - Where did the ball Pitch? (if outside leg stump means not out)
2) I - What did it Impact? (must not be bat or hand holding bat)
3) P - Where's the Point of Impact? (See explanation below)
4) S - Would it have hit the Stumps?