Visual effects are used in post-production to enhance films and achieve things that would be impossible to film directly. They range from simple speed adjustments to complex effects like aliens attacking. Editing is also vital in post-production, allowing editors to cut clips and rearrange footage. The document outlines the basic panels and functions of Final Cut editing software, including the browser to view footage, timeline to arrange clips, and canvas to view the edited video. It provides instructions for applying a letterbox effect to make films look more professional.