Video editing involves rearranging and combining video shots to tell a story in a coherent manner. The key purposes of editing include storytelling, controlling pace, combining different shot types, and following conventions like the 180-degree rule for continuity. Specific editing techniques discussed are match cuts, shot reverse shots, fade ins and outs, and using speed changes like slow motion for dramatic effect and fast motion for comedy. Proper editing sequences shots smoothly and makes the edits invisible so the audience follows the narrative.