Clearing the RTOS confusion

What is RTOS?
Real-Time Operating System or RTOS is an operating system designed for use in a real-time computer system.
It changes task priorities instantly and allows data to be processed rapidly enough such that the results can be used in response to another simultaneously occurring process.

What is mutex?
Short for a mutual exclusion object.
In computer programming, a mutex is a program object that allows multiple program threads to share the same resource, such as file access, but not simultaneously.
When a program is started, a mutex is created with a unique name. Then, any thread that needs the resource must lock the mutex from other threads while it is using the resource. The mutex is set to unlock when the data is no longer needed or the routine is finished.
This is particularly useful in concurrent programming to better utilise multi-core architectures.