Amplification via a NPN bipolar transistor.
In this part of the little Arduino adventure, I've been messing around with the Fritzing prototyping application. This lets you design things based on bread board layouts, then to generate Schematics and PCB. Unfortunately I couldn't get the schematic to draw properly. Some connections are missing or wrong. But that's ok, I'm not using it for anything serious :) Behold some pretty screenshots! Schematic... slightly wrong. Bread board diagram made in Fritzing.