A grandstand is a large and normally permanent structure for seating spectators, most often at a racetrack. This includes both auto racing and horse racing. The grandstand is in essence like a single section of a stadium, but differs from a stadium in that it does not wrap all or most of the way around. Grandstands may have basic bench seating, but usually have individual chairs like a stadium. Grandstands are also usually covered with a roof, but are open on the front. They are often multi-tiered.
In the United States, smaller stands are called bleachers, and are usually far more basic and typically single-tiered (hence the difference from a "grand stand"). Early baseball games were often staged at fairgrounds, and the term "grandstand" came along when standalone baseball parks began to be built. A covered bleacher may be called a "pavilion", also to distinguish from the main "grandstand".
The pejorative verb "grandstanding" is often applied to politicians or other public figures perceived to be over-acting, i.e. "playing to the grandstand".