Transistors are used in circuits as a switch to control the flow of electricity through different parts of the circuit.
Diodes are an electrical component that only allows current to flow in one direction. Diodes can be used as switches, gates and in the case of light-emitting diodes (LED), to produce light in a circuit.
Coils are used to create an electromagnet field.
Integrated circuits contain an entire electrical circuit on one chip. Integrated circuits keep pushing technology when the size of components can be made smaller.