\r is carriage return (moves the cursor horizontally back to the the left of the page)
\n is new line (moves the cursor down one line)

They’re anachronisms from the typewrite age: you could press ‘enter’ and drop the cursor down to the next line on the page (actually it raised the paper instead, but same result)

However you had to, in many models, manually grab the carriage (the bit that moved across your page as you typed) and push it back over to the left. On many models there was a bell that chimed when you were approaching the right margin of your page, signaling that you should end your word, press enter (\n) and then return the carriage to the starting position on the left margin (\r).

It would appear that some people did this in a different order, as the classic ordering of \r\n (or 13 followed by 10, in ASCII), is carriage return first, followed by the newline.

I’d be interested to hear if anyone knows of why it’s \r\n (13,10) instead of \n\r (10,13).