What is an overlay and what can I use it for?

Adding an overlay means adding a clip or a picture to your video that appears as a separate layer. All overlays are located on the top track on the timeline. With an overlay, you can do the following:

1. Create Picture-in-picture, adding a smaller picture or clip within the larger frame of your video, or adding a split-screen by positioning two pictures or clips side-by-side on the screen - check this article
2. Overlap two pictures or videos and adjust their opacity
3. Use masking to create effects such as cloning, adding or removing objects, and so on
4. Create a green screen effect by using the Chroma Key feature