A board is a square piece of wood or stiff cardboard that you use for playing games such as chess.
(棋) 盘 • ...a chequers board. …一个跳棋盘。
When you board a train, ship, or aircraft, you get on it in order to travel somewhere.
登上 (火车、船或飞机) • I boarded the plane bound for Boston. 我登上了飞往波士顿的航班。