Drywall is the smooth wall material used inside most modern buildings. If you tap on the walls in your home or school, you're probably touching drywall: large flat panels made of chalky white gypsum pressed between two sheets of thick paper.

Before drywall became common in the 1950s, builders created walls using lath and plaster, a slow, skilled process that took days to complete. Drywall changed construction by making it much faster and cheaper to build houses and offices. Workers can hang and finish drywall panels in hours instead of days.

You might also hear it called wallboard, gypsum board, or by the brand name Sheetrock. When you see a room being built, those big white or gray rectangles getting screwed into the wooden frames are drywall panels. After installation, workers spread joint compound over the seams and screw holes, sand everything smooth, and then the wall is ready for paint.

Drywall dents and tears fairly easily compared to plaster, which is why a flying baseball or a doorknob can punch a hole in it. But that same softness makes it easy to repair and replace.