In a post on his Medium blog Cameron Nokes explains the two most important processes in any Electron app: the main process and the renderer process.

Central to Electron is the concept of two or more operating system level processes running concurrently — the “main” and “renderer” processes. Dealing with multiple processes is new territory if you’re coming from browser Javascript land. It was definitely a paradigm shift for me initially, and working with multiple processes may mean you make different design choices in your app that you wouldn’t otherwise.