Is there a difference between
\ldots, the ellipsis?
If yes: Which? When to use
\dots and when to use
If no: Why are there both at all?
\ldots is equated (
\dots. so in text, it's the same, and you can use either.
amsmath, the situation is more complicated;
\dots tries to determine by context (only in math mode) whether to use
\cdots, with several more options for the author if
amsmath doesn't get it right.
so in general, it's easier to just use
\dots and not have to remember the details. but if the alternative chosen by
amsmath isn't appropriate, the original commands can still be used explicitly.