Intro
There’s no clear definition, but here’s what I’ve read in various sources. EmbeddedSystems is the domain of programming in which hardware and software are combined to complete a limited number of tasks, often using real-time data and input, as part of a larger system.
Abstraction
An embedded system, usually, runs without interference from the user, it serves a specific purpose and/or function within a larger system, but in a manner that’s abstracted and hidden from the user.
A great example I can think of is the ECU of car’s engine. That’s a system that’s working with all sorts of input and is responsible for many functions; but ultimately is only a part of a car. It’s an entire system embedded within the car.