Transistors are the fundamental building blocks of modern electronics. They are primarily used to both switch and amplify electrical power in circuits. Aside from being integrated into circuits, they can also be used and packaged individually.
Transistors were invented by John Bardeen, Walter Brattain and William Shockley in 1947. Prior to transistor development, electronics were very large to compensate for electrical flow. Therefore, very few appliances could be useful or convenient in homes and schools. Integrated circuits allowed for electronics, such as computers, calculators and radios, to be made much more compact and suitable for use in homes.
The main property of transistors that allow them to be useful is called gain, which allows the transistor to receive and send very large signals from its very small terminals. They can also effectively be used as a switch to turn electrical signals on and off. The difference between transistors and switches is that a transistor can allow other current, which can be determined by circuit properties, and switches cannot. Finally, its terminals can receive very small or weak signals and output them at much higher levels, effectively working as an amplifier. Due to their multipurpose design, small size and cheap cost, transistors effectively popularized electronics for modern use.