Each line in a Windows/DOS text file normally ends in both a Carriage-Return and Line-Feed character; this <CR><LF> pair is considered the normal “newline” character even though it really is two characters. At the end of a line, Pressing the Delete key once deletes the <CR><LF> pair. Similarly, pressing the Enter key (in Insert mode) inserts a <CR><LF> pair.
If a text line ends in just a Line-Feed when the file type is set to “0=DOS text”, <LF> is displayed at the end of the line. Such a line may be corrected by deleting the lone <LF> by pressing the Delete key and then inserting the <CR><LF> pair by pressing Enter.
UNIX text files normally have lines ending in just a Line-Feed character, which is therefore the “newline” character. Pressing the Enter key inserts only the Line-Feed character. Carriage-Return characters have no special meaning, and are displayed as <CR>.
More info over converting Windows to UNIX.
More info over converting UNIX to Windows.