1. I want to learn RTOS with TI's TM4C board. I use Keil.
2. I had searched on net & checked that freertos is used very frequently.
3. What is best way to learn freertos. (I have to learn to basic of rtos also)
There is book on freertos website, is it right place to start?
Or any suggestions for that.

 

Chapters 1 and 2 of the Salvo RTOS manual have a good introduction to RTOS fundamentals. Looking through the particular examples would help. But if you are going to use freeRTOS, you should get its manual and any tutorials and read them.

A good first project is to flash an LED under RTOS control. That will get the sysTIK and basic scheduling working as well as just being able to compile the OS and make a task.
Then flash 2 LEDs using separate tasks.
Then add a button task that sends a message to one of the LED tasks to turn it on or off.
Then use a semaphore to sync the LEDs.

If you get that far, you'll be well on your way.

Good luck.

EDIT: if you can, find an old copy of any operating system text by Peterson or Andrew Tennenbaum (sp?) Either covers OS fundamentals in a readable format which will help you understand RTOS fundamentals. MicroC/OS-II by Jean J. Labrosse is good as well. Used copies of these books are available for cheap.