Difference between line and blackboard in Korean
선·칠판
선line
The word "선" means "line." It is used for a straight mark on paper, a board, a map, or the ground. In school, you often use this word when you draw a line or look at lines in a notebook.
칠판blackboard
A blackboard (칠판) is a dark board that people write on with chalk. You usually see it in a classroom at school. We use this word when talking about lessons, teachers, and things written for students to read.
The difference
A 선 is just a mark or shape, like a straight line drawn on paper or on a board. A 칠판 is the whole board itself, not one thing drawn on it.