A process is a unit of work on a Linux system. Each program you run represents one or more processes, and Linux provides commands for viewing and manipulating them. Every process is identified by a numeric process ID, or PID.

Processes are different from jobs (see Shell Job Control): processes are part of the operating system, whereas jobs are higher-level constructs known only to the shell in which they’re running. A running program comprises one or more processes; a job consists of one or more programs executed as a shell command.