Unix identifies each process with a unique integer called ProcessID. The process that executes the request for the creation of a process is called the 'parent process' whose PID is 'Parent Process ID'. Every process is associated with a particular user called the 'owner' who has privileges over the process. The identification for the user is 'UserID'. The owner is the user who executes the process. The process also has 'Effective User ID' which determines the access privileges for accessing resources like files.
getpid() - process id. getppid() - parent process id. getuid() - user id. geteuid() - effective user id.