Dirt

Dirt is a basic block found abundantly in the Overworld.

Coarse Dirt is a variation of dirt that will not grow grass.

Obtaining
Dirt will drop as an item when broken with any tool or by hand, but a shovel is the fastest way to break it.

Natural generation
Dirt is found at any altitude, and comprises the majority of the upper terrain layers in most overworld biomes.

There are approximately 1,850 dirt per chunks in Plains, Forest, Tundra, Jungle, and Extreme Hills biomes. There can be as many as 3,000 in chunks with high mountains.

Coarse dirt can be found in Mega Taiga, Mesa and Savanna biomes.

Dirt based blocks
When grass, mycelium, or podzol are broken using a tool that is not enchanted with silk touch, it will drop dirt.

Farmland will drop dirt when broken. It will also turn into dirt if either a mob jumps on it, or if nothing is planted on it and it is not within four blocks of water.

Usage
Dirt's primary use is for farming, but it can also be used as a highly available building block.

Farming
Dirt and coarse dirt have the ability to grow saplings, sugar canes, and mushrooms can be planted directly in dirt under appropriate conditions will.

Using a hoe on dirt will turn it into farmland, enabling wheat seeds, pumpkin seeds, melon seeds, potatoes, and carrots to be planted on it. If you use a hoe on coarse dirt, it will turn into dirt instead.

Grass and mycelium spreading
When a dirt block is adjacent to a grass block and is exposed to a light level of at least 4, it will eventually be converted into a grass block at random intervals.

Mycelium spreads in similar fashion, but requires a light level of at least 9.

Neither mycelium nor grass will spread onto coarse dirt.