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CRLF = Carriage Return Line Feed

It refers to the old typewriters.
Carriage with the print head at the end of a line (or at the most right position that the machine allows), bringing it back to the left of the machine and scroll the paper 1 line up so the next line can be typed.
With later typewriters it was the platen the was in the most left position and had to be brought back to the most right position with a carriage return lever.

It is not always noticeable, but I had typing lessons as a kid ;D