Sheetrock is a brand name for drywall, the smooth white or gray boards that cover the inside walls of most modern houses and buildings. If you've ever seen workers building or repairing a house, you might have noticed them carrying large, flat panels and screwing them to the wooden frame. Those panels are sheetrock.

Before sheetrock became common in the 1950s, builders covered walls with plaster, which required skilled workers to spread wet plaster over wooden strips and wait for it to dry. This process took days and required real craftsmanship. Sheetrock changed everything: workers could put up walls in hours instead of days, making houses faster and cheaper to build.

The boards come in huge sheets (usually 4 feet by 8 feet) made from a layer of gypsum, a soft mineral, sandwiched between two sheets of heavy paper. After workers attach the panels to the wall frame, they cover the seams with tape and a paste-like substance called joint compound, then sand everything smooth. Once painted, you can't tell where one sheet ends and another begins.

Like how people say “Kleenex” for any facial tissue, many people use “sheetrock” to refer to any brand of drywall. The generic term is drywall or gypsum board.