Were there answer choices from which to choose? If so, please share them next time.
The Pythagorean Theorem would suit very well in finding this distance.
The horizontal distance between the two points is 2 (I'm neglecting the - sign), and the vertical distance is 4. Thus, the distance between the two points is
A line segment has two endpoints unlike a line where a line is infinite with no end! :) Think of a line segment essentially just being two points on a line. :)
