Windows uses \r\n for newlines, Unix uses \n, old Mac used \r. This "newline" problem has caused no end of headaches!
When This Matters
When you open a file created on Windows in a Unix text editor, you get weird ^M characters. The newline converter fixes this by converting between formats.
If you've ever had a "broken" text file that looks wrong in your editor, a newline converter can fix it instantly!