A chalk board
is a large, flat, dark, slightly abrasive surface
on which you write
, which is a material that crumbles
easily and hence rubs into the irregularities of the board, producing lines. The advantage
to chalk boards is that they are easily erased using a felt eraser
Some people are allergic to chalk dust, so they use a whiteboard instead. Chalk boards are commonly found in classrooms, meeting rooms, and other places where a topic being dicussed can be described with drawings.