Some of the items you will need to remember.
-Diodes allow current to flow in only one direction.
-The leads on a diode are called an anode (+) and a cathode (-). The cathode is identified with a stripe.
-Transistors are capable of using a voltage or current signal to control current flow and can act as amplifiers or switches.
-A Bipolar junction transistor has three leads. They are the base, emitter, and collector.
-A field effect transistor, or FET, has three leads as well. They are the gate, source, and drain.
If you have all this you should be fine with this section. Explanations of semiconductors on the internet tends to be a bit complex. If you are looking for more information about semiconductors, or electronics in general, I recommend the book Understanding Basic Electronics published by the ARRL. This gives down to earth and simple explanations of some fairly complex electronics subjects. This book does not presume you have any previous knowledge of electronics and builds from the ground up. A great book!
Until next time and lesson 21...