[racket] ... vs ...+

This might be a silly question, but in the docs, what's the difference
between ... and ...+?
A good example for that is the definition of begin:
(begin<http://docs.racket-lang.org/reference/begin.html#(form._((quote._~23~25kernel)._begin))>
 form ...)(begin<http://docs.racket-lang.org/reference/begin.html#(form._((quote._~23~25kernel)._begin))>
 expr ...+)
Is there anywhere I missed where this is explained?

And on a completely unrelated note, if I find a typo or small grammatical
mistake in the docs, what should I do about it? Should I send an email about
it, or is there somewhere where I can fix it myself?
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