A board used in classrooms (or similar places) on which you write with chalk and erase — a blackboard/chalkboard.
教室の黒板に今日の予定が書いてある。
The schedule for today is written on the classroom blackboard.
先生はチョークで黒板に線を引いた。
The teacher drew a line on the blackboard with chalk.
黒板を消すために消しゴムを貸してください。
Please lend me an eraser to erase the blackboard.