A process is an instance of a program in execution. It is seen as a live, runtime schedulable entity by the OS. In other words, it's the process that runs when we launch a program.
The OS, or kernel, stores metadata about the process in a data structure in kernel memory; on Linux, this structure is often called the process descriptor—though the term task structure is a more accurate one. Process attributes are stored in the task structure; the process PID (process identifier) – a unique integer identifying the process, process credentials, open-file information, signaling information, and a whole lot more, reside here.
From the earlier discussion, Virtual memory, we understand that a process has, among many other attributes, a VAS. The VAS is the sum-total space potentially available to it. As in our earlier example, with a fictional computer...