What is "box-drawing character"

n. a character used for creating boxes.

Box-drawing characters, also known as line-drawing characters, are a form of semigraphics widely used in text user interfaces to draw various geometric frames and boxes. In graphical user interfaces, these characters are much less useful as it is much simpler to draw lines and rectangles directly with graphical APIs. Box-drawing characters work only with monospaced fonts; however, they are still useful for plaintext comments on websites.

Used along with box-drawing characters are block elements, shade characters, and terminal graphic characters. These can be used for filling regions of the screen and portraying drop shadows.