OBS VirtualCam is an OBS Studio plugin which allows you to output the output of OBS Studio to a virtual camera device.

OBS Studio is free open source software which allows you to do many interesting things to video Using OBS Studio (free) with Snap Camera (free) or ChromaCam ($29.99 lifetime license) you can easily put yourself in your own presentations in such a way that it will work on almost any medium you would like to present on without having to invest in a green screen. Sometimes though you do not have that available or want to be able to do more than what the tool you are using provides.

Various tools provide features which help you achieve that, for example Microsoft Teams. When giving online presentations, it helps for personal marketing if people can see you on the screen.