OpenURL is a standard for gluing together metadata about a resource such as a journal article into a single URL. The purpose of this is so that any OpenURL compliant resolver knows how to pick such a URL apart, and use whatever kind of magic it has access to in the pursuit of finding something useful for the user - often the full-text of the referent, of maybe a holidings record in a local library.
OpenURL caught on largely because it was so simple. The original specifications (now known as version 0.1)
Fish and frogs.
Fish and frogs.
Fish and frogs.