Difference between hard real-time and soft real-time

What is the difference between hard real-time and soft real-time OS?

Critical task completion on time is guaranteed by a hard real time system. The tasks needed for delays in the system are to be bounded by retrieving the stored data at the time which takes the operating system to complete any request.

A critical task obtains a priority over other tasks and maintaining that priority until the completion of the task. This is performed by a soft real time system. The system kernel delays need to be bounded as in the case of hard real time system.