Grass is a vanilla minecraft block, which covers a large portion of the surface of a randomly generated world. When it is broken, it drops a Dirt block. It mainly covers the floor of biomes such as Forest, Plains, Swampland, Jungle, Taiga (under the snow), and Extreme hills.
It takes 0.75 seconds to break one grass block by hand, 0.4 seconds with a Wooden shovel, 0.2 seconds with a Stone shovel, 0.15 seconds with an Iron shovel, and 0.1 seconds for both a Gold shovel and Diamond shovel, so if you are looking for speed, choose Gold or Iron, but if you are looking for endurance AND speed, choose Diamond.
To obtain a grass block, you will need a Shovel/Pickaxe with Silk Touch enchantment, as said before when normally dug a grass block will drop a Dirt block. However, 2 UU-Matter can create 16 Grass Blocks. You can also use a Alchemical Tome in a Transmutation Tablet to obtain it.
Sometimes Tall Grass can spawn on top of grass blocks naturally or with right clicking a Grass block with bonemeal. Bonemeal can also spawn flowers.
When a sheep is sheared, to grow back its wool coat it needs to 'eat' the grass from a grass block, turning it into a Dirt block. It will come back, as a corresponding nearby Grass Block will spawn grass back onto the dirt.
You keep the Ring in the recipe below.