What exactly do they do? How do they work?

 

WOW, that’s a much bigger question then I think you realize. In short, A transistor is a semiconductor device that uses a change in voltage at the BE (base, emitter) junction to control current flow through the CE (collector, emitter) junction. NOTE-Uses voltage to control current. It is in fact more complicated then that, but I’m not a teacher, so I would probably confuse you (and me) more if I tried…

I added a pic of a transistor so you can see where the BE and CE junctions are.

Edited: Apeiron is right! This is why I’m not a teacher. Brain not work to well in the morning time.

 

A bipolar transistor like you've described uses current to control current. A field-effect transistor uses voltage to control current.

 

They dress up in funny clothes and try confuse drunk fellars. Them bipolar ones are the worst. They'll hit on your girlyfriend too.

 

Ill be verry frightend the day a electrical component hits on my girlfrend!!! ..

 

Your garden variety transistor does one of two things. It either acts like an amplifier or it acts like a switch. In its nature it is a current amplifier, but with a handful of components around it that may be changed so the end result is voltage amplification. Some transistors are designed to work well as switches so you can use a small amount of power to switch a larger power, somewhat like a relay. If it is something that interests you Radio Shack carries an excellent introductory electronics book written by Forest Mims. It will give you a brief but reasonably complete explanation. They are a complex device that takes most of a college text book to outline how they actually work.

 

Bah.. I could do it in a couple pages.

 

Really, I'd like to read it!