I am a beginner in the field of embedded systems. I don't know how to begin? Do I have to study microprocessors at first or not? I want an advice, a tutorial or a book for beginners in this field.
An embedded computer than has a full operating system such as Linux. These are usually not real time, but can be sort of real time. It is easy to add network connectivity and so forth, either wireless or wired. Look at systems from TI for low power wireless.
An embedded computer that has either no operating system (you handle everything) or a basic RTOS which is very small. The interface choices are more limited, but it will be lower power and very predictable.
An embedded system controlled by an FPGA.
For any of them, select a starter kit with user friendly instructions. Some links to start looking:
full OS https://www.google.com/search?q=linux+embedded+board&gws_rd=ssl