An ORCID identifier is like an ISBN, or a DOI, but for an author, editor or other contributor to literature, to research - or to Wikipedia.
For example, say you're reading a paper by William Smith. How do you know whether that’s the William Smith whose reputation you trust, or a namesake you don’t, or one you’ve never heard of? How can we associate and catalogue works by “William Smith”, “W. B. Smith”, “Bill Smith” and so on, when they’re all by the same person – indeed, how do we tell whether or not they are by the same person? What happens if he becomes William Smith-Jones upon marriage, or takes a completely different name on changing of religion? ORCID IDs solve that problem.
GLAM Wikipedians and their editing-trainees may register for an ORCID ID, to disambiguate themselves from others with similar names, and to associate their contributions with any academic or public outreach authorship. Registration is free, at http://orcid.org/
ORCIDs can then be displayed on user pages, and may also be added to articles about people including of course GLAM staff and academics. See WP:ORCID, or contact Andy Mabbett, Wikipedian in Residence at ORCID, for details.