The word board has several distinct meanings:

1. A flat, rectangular piece of wood or other stiff material. Carpenters use boards to build houses, fences, and furniture. You might nail boards together to create a treehouse floor, or paint on a board in art class. A diving board is a springy board that extends over a swimming pool. When something is covered with boards, like a window in an abandoned building, we say it's boarded up.
2. A group of people who make important decisions for an organization. A school board decides policies for the school district. A company's board of directors guides major business decisions. Museums, hospitals, and charities all have boards. These groups typically meet regularly to discuss problems, review progress, and vote on significant choices. When someone joins a board, they take on responsibility for helping the organization succeed.
3. To get onto a ship, airplane, train, or bus. When you board a plane, you walk through the door and find your seat. Flight attendants might say, “We're now boarding rows 15 through 30.” Pirates in old adventure stories would board enemy ships by swinging across on ropes. The phrase all aboard means everyone should get on because the vehicle is about to leave.
4. A flat surface used for a specific purpose, like a chessboard, bulletin board, whiteboard, or skateboard. Each type of board serves its own function, but they're all flat surfaces designed for particular activities.