What are 'track mats' used for?

Track mats are an essential tool in video editing and compositing that allow for the creation of complex effects. They serve as masks that dictate which parts of video layers are visible based on their alpha channels. By placing a track mat above another clip on the timeline, you can control the transparency and visibility of that clip, enabling dynamic and intricate visual effects. This capability is pivotal in tasks such as layering graphics, creating transitions, and applying effects selectively, thereby significantly enhancing the overall composition of a scene.

Using track mats can also simplify workflows, allowing editors to achieve intricate looks without the need for extensive keyframing or multiple adjustment layers. They provide a powerful method for combining different elements in a visually appealing way, making them a fundamental aspect of professional video editing practices.