Steve notes that Excel allows saving a worksheet in several different CSV formats. He understands the differences between most of the variants, but he’s at a loss as to the difference between the “CSV (Comma delimited)” and “CSV (MS-DOS)” formats.
For most people there is very little difference between these two versions. (There are much bigger differences between these versions and the Macintosh CSV version, which Excel also supports.) The reason is that there is little difference between what the two formats create. With most data, you could create a file in the two formats and compare them byte-for-byte and find no differences.
The difference between the two is important, however, if you have certain special characters in text fields; for example, an accented (foreign language) character. If you export as Windows CSV, those fields are encoded using the Windows-1252 code page. DOS encoding usually uses code page 437, which maps characters used in old pre-Windows PCs. If you export as one and then import with a tool that expects the other, most things will look fine but you’ll get unexpected results if, for example, you know someone with an umlaut (or other foreign character) in their name.
Essentially, CSV comma delimited is used by Windows and CSV MS-DOS is used by older DOS-based operating systems and you would rarely encounter issues except in the circumstances outlined above.
Additional information on code pages can be found at this Wikipedia page: