Welcome to Minecraftia, Judge!
Rock also immediately turns to cobblestone as soon as you dig it up.
Dirt - soft block that you can plant trees, wheat, and flowers on.
Gravel - Chunks of small pebbles that actually obey gravity. Very easy to dig through (i.e down stand under them while you dig). For about every ten blocks of gravel you dig you get a piece of Flint, which can be used to make a firestarter, or arrows.