This is a simple description of what a transistor is and how it is used.
Regarding the word 'Transistor' and the word 'Transfer:' It is true that the word transistor was an abbreviated version of the words 'Transfer Conductance Varistor.' I discuss this in my video at www.youtube.com/watch
. However, please understand that I started teaching this and scripting this video over 20 years ago. There was no Wikipedia, or internet for that matter, and if you think the transistor explanations you see today are hard to get through, all I had to work with was old books and lecture notes from the library. I read that the transistor got its name because it "transformed input signal into output resistance," and I therefore thought of it as a Transforming Resistor from then on.
Even after learning the true derivation of the word, I continue teaching it using Transforming Resistor for several reasons. First, when you say it's a Transfer Varistor, the student then wants to know WHAT is being transferred. The correct answer is "charges," and then the student asks what do you mean by "charges," and then that's 3 hours of your life gone trying to explain how electricity REALLY works (see my video www.youtube.com/watch
for more details).
Second, the word 'transistor' was invented by Bell Labs to describe bipolar junction transistors, which work by transferring charges across the reverse-biased collector-base junction. Field effect transistors do the same kind of job (variable resistor) as a BJT, but there is no transferring going on, but they still call it a transistor for some reason. I'd rather set aside the word 'transfer' and keep using my version, transforming resistor. I don't mean to try and change history here, but my version makes things a little easier to understand for the beginner. It's a bit like the midnight ride of Paul Revere; everyone knows that a rider went far and wide, warning that the British were coming, but in fact there were three riders (one of whom was Revere), and Revere was actually captured by the British early on, and one of the other guys actually saved the day. However, the story about Paul Revere is a better story, so that's the one that everyone remembers.