IIIF (International Image Interoperability Framework) is a set of APIs designed to operate with the storage and presentation of digitized objects via a web-based interface. They are designed to be of particular use to archives, museums, and libraries that provide online images (of paintings, scanned historical documents, etc.) for public viewing. Version 2.0 was announced on September 11, 2014. (Pre-release versions of the 2.0 image and presentation specs were, for some reason, apparently code-named "Voodoo Bunny" and "Triumphant Giraffe" respectively.)
There are actually two APIs under the umbrella of IIIF, an image API and a presentation API (originally Metadata API). The image API is designed to do graphic manipulation "on the fly" through a Web interface; the API features allow the images to be viewed and downloaded in a variety of graphic formats, resolutions, rotations, croppings, and so on. The presentation API has broader goals regarding the representation and presentation of all the aspects and metadata of a digitized object from an archive or museum.