Grass is a tile which grows out of the ground and provides food for grazing animals. Both Cows and Sheep can be found on grass, which eat the grass. After the grass is eaten, the tile gets down to ground level where over time it slowly grows back up to its full height.
Due to the nature of the grass itself, buildings can't be built on any grass tile.
While you can use a Scythe or a Sickle on some grass to cut it down to look in appearance like it has just been eaten like is done by the animals, that produces no actual resources through that action.
Cows will produce some dung after eating 10 tiles of grass, and after producing three pieces of dung will become full with a milk bottle icon appearing above their heat. A bucket can be used on a cow to collect milk, which in turn can be put into a milk storage building.
Sheep will eat 20 tiles of grass before they have a shearing icon flashing above them, at which point you can use some shears to collect fleece. That fleece can then be used to make wool using a spinning wheel, which in turn can be used to make clothing.
After being eaten, it takes 15 seconds for grass to grow back. Dung will prevent grass from regrowing.
In previous versions it was necessary to build a fence around animals who were grazing if it was next to an areas where you are growing cereal on a cereal crop tile, as the animals will eat the harvested cereal and interfere with the production of that grain crop. That behavior was removed with version ???
Grass • Regular Land Tile