RTOS, is a realtime operating system which means it is processing realtime not with a delay. On the fly. There are RTOS kernels available that have been verified and bought off-the-shelf requiring no verification of the kernel because it has been done for you. It is ready to use and comes with the processor. If you have a processor board or embedded processor, you can use a free RTOS or make your own. But you have to do the whole verification and it is not off-the-shelf.
Hardware and software advisor for tech startups. ASIC, FPGA, RPi, Arduino, AI, robots, drones, blockchain, Machine learning, vision processing, IoT and 3D printers are my fields of expertise.