linux users, specially those coming from Windows, are often not familiar with how processes or jobs or running applications are prioritized. Linix schedules an application's execution depending on its priority. Linux comes with a command that modifies an application's priority and it is called "nice".
"nice" is often invoked by appending "nice" to how an application is invoked. For example, "nice HBTest -i /cdrom/VIDEO_TS/*", this gives the application HBTest a lower priority.
This is useful when you are sharing the system with other users or simply want to run an application without slowing down the entire system. For example, ripping a DVD using HandBrake whilst surfing the internet.