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:

• 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
• Overlap two pictures or videos and adjust their opacity
• Use masking to create effects such as cloning, adding or removing objects, and so on
• Create a green screen effect by using the Chroma Key feature