Lawn grasses fall into two general categories: cool-season and warm-season. Each group comprises a wide variety of grasses. Water and fertilizer needs differ between the two groups, and susceptibility to some pests and diseases varies as well. Where you live usually dictates the type of grass you can grow, although cool-season sorts succeed in many areas if given sufficient water.
Most lawn grasses spread by creeping stems growing either aboveground (stolons) or below ground (rhizomes). As the stems advance, they send up shoots, ultimately producing a thick, carpetlike turf.
Unlike almost all other plants, grasses grow from the base, not the tip. After you mow the lawn, the grass blades renew their length from the root end, or new blades sprout from the base.
Like many other plants, grasses prefer a sunny location. If you're considering planting lawn in a deeply shaded area, think first about alternatives. Could the area be covered with nonplant material, such as decorative bark or stone? Would a shade-loving ground cover be a satisfactory substitute for grass? If a lawn is still your top choice, decide how to let as much light as possible into the area; you may be able to thin the canopy of a tree or remove low-growing branches, for example. Given more sunlight, the lawn will be thicker, have fewer weeds, and be better able to resist diseases and pests.
Some grasses handle shade better than others; tall fescues and St. Augustine are good choices. Consult a local nursery that carries a wide variety of grasses (both seed and sod) for a list of hybrids best suited to shade.
Let grass in shady conditions grow about an inch higher than you would if it were in sun; this compensates for the plants' reduced ability to manufacture nutrients in low-light conditions. Be sure to water regularly and fertilize at the rate recommended for the particular grass.