The description of the arXiv is a little off, it says "Cornell's library of published academic research papers", while really the arXiv is mainly for preprints,

The description of the arXiv is a little off, it says "Cornell's library of published academic research papers", while really the arXiv is mainly for preprints, i.e., papers that have not yet been published. It is true, however, that in some fields it is common for journals to let you keep a (non-final) version of your paper on the arXiv.