Process--A program in execution. It's the unit of work in a modern time-sharing system.
Process includes these things, process stack, data section, heap, text.
A program by itself is not a process. A program is a passive entity. A process is an active entity.
A program becomes a process when an executable file is loaded into memory.
Although two processes may be associated with the same program , they are nevertheless considered two separate execution sequences.
Only one process can be running on any processor at any instant.