I was looking at my Raspberry Pi recently, and noticed strange spikes protruding on the top of it (They are the ones next to the yellow input thingy)
What are they used for? What is their purpose?
You are referring to the general purpose I/O lines (or GPIO). You can do all sorts of things with them. Basically they are for reading sensors and activating additional electronics such as motors, actuators, solenoids, other digital electronic circuits, etc.
You can find allot of interesting things about the Raspberry Pi in this PDF
And this a great reference for the GPIO HEADERS pin numbers and their functions.
There is a great deal of detail on elinux about them here, as well as a fairly large list of boards which plug on top of them to add more features for the Raspberry Pi here.
They are a great way to make first steps from programming on its own into software controlling hardware (talking to electronics).
