Grass
Grass is the common name given a whole variety of plants, that technically, should be restricted to monocotyledonous plants in the family Poaceae. These true grasses include most of the plants grown as cereals, for pasture, and for lawns. Grasslands, or prairies, are habitats that are marked by open expanses of grasses.
Grasses also include some more specialised crops such as the herb, lemongrass, as well as many ornamental plants, and some weeds. They also include plants often not considered to be grasses, such as bamboos.
Grasses in garden design
Various types of grasses are often used in creation of gardens, both shade and sun, typically serving the purpose of a ground cover. In addition, some tall grasses, such as Miscanthus sinensis (common name of Zebra Grass) are used to serve a more plant-like role rather than a ground cover in garden design.
Lawns
A large amount of property owners own land in addition to their own building, and rather than cover the land with plants, choose to use grass instead. A lawn can consist of one or more of the various types of grasses, and usually covers a moderately large portion of a given yard.