>>1829Linux has always had the ability to be a real time OS. A real time OS ensures low latency in kernel space. Here is the best way to think about it;
You know how a guitar works? Imagine a guitar plugged into a computer via an audio interface. With a normal mainline kernel there might be a slight delay when you strum the guitar. You have headphones plugged into your DAC and are strumming the guitar. With a non-real time kernel there might be a several millisecond delay delay between your strumming and when you hear the notes in your headphones.
With a real time kernel there is no delay. When you strum you will hear the notes at the exact same time.
Real time Linux kernel have been a thing for decades. They form the basis of all the multimedia/digital audio workstation distros. This e-celeb or whoever (I didn't watch the video) is just going over information everyone that works with this type of software has known for years. Maybe they finally merged the patches into mainline or something. I dunno.
The trade-off with a realtime kernel is the fact that it can cause high CPU usage in some cases. For the vast majority of users a realtime kernel isn't needed and can cause various issues with day-to-day stuff.
Realtime kernels are mainly used for things like I mentioned above (multimedia production) or for other tasks where realtime is vital to functionality (imagine a fighter jet with a stick hooked up to a small computer that controls the flaps). If you want to know more read about Real-time operating systems on wikipedia. The vast majority of them are not UNIX based and are small OSs geared towards specific tasks running on small computers.