Electrons spin around the more sedentary constitutes of atoms. Electrons can be tempted out of their orbits to join with billions of other electrons in a flowing current. When the flow comes to a fork in the path, most electrons will go in the path of least resistance. In some cases, the electrons will pile up. Sometimes, the electrons will react with magnetic fields. Whenever a current flows through wire, a magnetic field is created around wire. Whenever a wire is moved through a magnetic field, a current begins flowing through the wire. Understanding the physics is fundamental to understanding the electronics.
Mathematics is the language for understanding electronics. If you are a beginner, learning Ohm's law can put power, current and resistance in perspective. Imaginary numbers, trigonometry and calculus all have important things to say about the behavior of electrons and the functioning of electronic components. Digital electronics has its own mathematics that deals with information processing. Boolean algebra is basic for an understanding of computer electronics.
One of the fundamentals of electronics is knowing how the basic electronic components work. You should learn how diodes, switches, resistors, capacitors, coils and transistors work. When these components are thoroughly learned, there are more complicated components that are built up from these simpler components. When you learn how these components work, look at how the components behave when exposed to alternating current (AC) and well as to direct current (DC). Sometimes the different responses to AC and DC can tell you a lot about a component.
Circuits appear when you connect components with wires and apply power to the assembly. There are some basic circuits every electronics expert knows: oscillators, amplifiers, rectifiers and radios. Basic digital circuits includes flip-flops, ring counters and programmable displays.
A solid foundation in the relevant physics, mathematics and electronics will make understanding systems easy. If you are interested in computers, digital electronics is a necessity. If you are interested in mobile phones, the analog part of electronics is important.