There are several different modes you can use when presenting.
Content only does not share a video of you.
Standout,
Side-by-side, or
Reporter mode share your video along with the content.
Click Add background to select a background for use in Side-by-side or Reporter mode
Content only - share the content only, no video of yourself
Standout - your video overlays the content
Side-by-side - your video is next to the content
Reporter - the content is in a window behind you, like a reporter