What is foul ball or foul territory?

Answer 1

Foul territory is that part of the playing field outside the first and third base lines extended to the fence and perpendicularly upwards.

A foul ball is a batted ball that settles on foul territory between home and first base, or between home and third base, or that bounds past first or third base on or over foul territory, or that first falls on foul territory beyond first or third base, or that, while on or over foul territory, touches the person of an umpire or player, or any object foreign to the natural ground.