Errata is simply the mistakes in printed music.  there is a repository of many of these mistakes maintained by the Major Orchestra Librarian’s Association (MOLA).  The mistakes and corrections are usually listed by instrument, rehearsal figure, measure number, beat, etc.  Some of these lists can be quite extensive however, failure to employ these errata lists may result in unnecessary time spent in rehearsals making these corrections.  This should be done in advance by the librarians.