This document covers key concepts about segments and congruence in geometry. It defines segments as parts of lines between two points and introduces the ruler postulate for assigning coordinates to points. The segment addition postulate states that if a point B lies between points A and C, then the sum of segments AB and BC equals segment AC. It also defines congruent segments as those with the same length and provides examples of finding lengths using the segment addition postulate and determining congruence. Homework problems at the end reinforce these concepts.