Screen sharing works in many video conferencing software packages but OBS gives you a lot more options. Frequently on Twitch you'll see the game taking up most of the screen, a video of the host overlayed on the video, with smaller areas showing parts of other windows, text, and videos. It also lets you save any number of these scenes and transition between them smoothly.

I was actually trying to get this working for myself because I'm doing a presentation in a few days and I'd like to be able to swap between myself full screen, and then either the slides or another piece of software with my face in a smaller area. If a "virtual webcam" tool was available for OS X I would be able to pipe that into Zoom.

I could just do a screen share and switch back and forth but I want to do something a little more polished.