Process Priority
A common type of scheduling algorithm is priority-based scheduling.
A higher priority run before those with a lower priority, whereas processes with the same priority are scheduled round-robin.
On some systems, processes with a higher priority also receive a longer timeslice
The Linux kernel implements two separate priority ranges.
Nice value A number from –20 to +19 with a default of 0. Larger nice values correspond to a lower priority—you are being “nice” to the other processes on the system. Processes with a lower nice value (higher priority) receive a larger proportion of the system’s processor compared to processes with a higher nice value (lower priority).
Real-time priority The values are configurable, but by default range from 0 to 99, inclusive. Opposite from nice values, higher real-time priority values correspond to a greater priority. All real-time processes are at a higher priority than normal processes.