In any home, there are lots of manufactured products: appliances, pipes, drywall, paint, lights, faucets, toilets, windows, shingles, doors, and much more. All of those products come together to create your new home.
The builder (or you as the customer) must specify a manufacturer for each of those items. Many people assume that a builder uses the least expensive items he or she can get away with (hence the term "builder grade"). But that's not usually the case.