Process (computing)

In computing, a process is an instance of a computer program that is being sequentially executed by a computer system that has the ability to run several computer programs concurrently.
A computer program itself is just a passive collection of instructions, while a process is the actual execution of those instructions. 
Several processes may be associated with the same program; for example, opening up several windows of the same program often means more than one process is being executed. In the computing world, processes are "formally" defined by the operating systems (OS) running them and so may differ in detail from one OS to another; for example in Microsoft Windows environment each instance of the same application is called a task.