<geek>A nice way of explaining compiling from source</geek>

From the install notes of qmail... ;)

If you're not familiar with the distinction between source code and binaries, imagine ordering a pizza delivered to your house. The "binary" version of the pizza arrives ready-to-eat. The "source code" pizza comes as a kit containing flour, yeast, cheese, sauce, toppings, and directions for cooking the pizza yourself. Source code installations are a little more work for you, but if you follow the directions carefully, the result is the same--or even better. The self-baked pizza will be fresher, you can adjust the toppings to your preferences, and you'll know a lot more about your pizza and how it "works".

Nicely put :)