Processes contains the program code and its current activity.
Depending on the Operating System (OS), a process may be made up of multiple threads of execution that execute instructions concurrently.
A computer Application is a passive collection of instructions, while a process is the actual execution of those instructions. Several processes may be associated with the same application; for example, opening up several instances of the same program often means more than one process is being executed.
Multitasking is a method to allow multiple processes to share processors (CPUs) and other system resources. Each CPU (core) executes a single task at a time.
For security and reliability, most modern Operating Systems prevent direct communication between independent Processes, providing strictly mediated and controlled Inter-Process Communication functionality.