The staging area where cars line up before going on track for a session. Drivers are arranged in order and released onto the track in a controlled manner, typically behind a pace car.
The Race Experience Rules define it precisely: "The Grid is the area of the track which the field is aligned prior to the session start." Grid order for practice is typically "on an as-arrived basis," and the rules warn that "cars that are not in position on the grid prior to the 1-minute signal relinquish their starting positions. They will be held behind other cars and must start from the back." The Pace Car Operations Guide adds that "the Pace Car should stage at a safe location adjacent to grid out. Between the five and one minute grid warning the Pace Car should proceed onto the track and prepare to be underway as the grid is released." Being grid-ready on time is a courtesy — late arrivals lose track time and may miss the session entirely.