A process is when a program is run. By keeping processes separated, it prevents the failure of one process from causing another to fail.
Newbie: It is a bad bad idea to make each little process that you have programmed or designed rely on another process. Sometimes it is necessary, but never suggested. Think of dominos. If one small process goes down, there is a good change that the rest are going to fail. Suddenly, one small failure has crashed your application, website, or process.