difference between DOS Format and MAC Format

When I save a file using nano on linux (bash), I get a message asking me to choose the format. There are two options: DOS Format and MAC Format. Can someone explain to me the difference between them?

Solution

If you just press enter and no option, you save it in the same file-format which was detected. (That is the third option, and the option to prefer for Linux.)

If you selected an option you can deselect it again with pressing again "Alt" & "m" for deselecting [MAC-Format] or "Alt" & "d" for deselecting [DOS-Format]. If there is no option selected you use the UNIX-Format "line flyback" (LF or \n), which is most likely the format to prefer on Linux. The selected option is written just before the file name in the bottom.