OBS
Open Broadcast Software Studio - more popularly known among video content creators across the internet as OBS Studio - is one of the most feature-rich open-source software available. The software is widely used by streamers, as it can not only record your desktop but can also be used for live streaming. It is also extremely versatile as it can be used with Windows, MacOS, and even Linux (although ut should be said that the Linux install is a slightly longer process; but we'll save that for a different Fast Track). OBS Studio is feature-rich to the point where it comes very close to simulating a live news studio as seen by news EPs in broadcast. That said, if used well, it has the potential to take your videos to the next level.
Why you must get it: 
OBS Studio has a ton of pro-level features. It has an easy-to-use settings panel that can help configure the software to fine-tune your videos. It also has a source-based audio mixer with plenty of audio filters to suppress noise, increase gain, or add audio modulation. The software also allows users to create scenes with real-time audio/video capture and real-time mixing. The scenes can be captured from multiple audio/visual sources - webcams, browser windows, capture cards, microphones, desktop audio 
and the like. Along with all that, OBS studio also allows users to do live transitions between multiple scenes; it has a Multiview mode where eight different sources can be monitored simultaneously; and a Studio Mode to preview the scenes and sources before making them live. It also allows for delay in streaming, giving the user time to add tweaks and corrections to the feed during a live stream. 

Special mention: Streamlabs OBS 
Designed mainly for gamers, Streamlabs OBS has a highly intuitive user interface with a customizable layout. On the downside, it's still in a beta stage of sorts, so it does take up more processing power and doesn't have MacOS support at this point.