This chapter begins with a brief executive summary of the nature and structure of the Crystallographic Information Framework data-exchange protocol. This has links to relevant extended documentation elsewhere in the volume, and acts as a concise reference for established users. The remainder of the chapter provides a more extended discussion for new users, orienting them towards an understanding of: the CIF format (and indicating the differences between the CIF 1.1 and CIF 2.0 syntaxes); the related Crystallographic Binary File (CBF) for storing binary image data; and the use of data dictionaries to hold well characterized tags identifying specific data items, and the dictionary definition languages (DDLs) used in CIF to store these. The mechanisms by which the International Union of Crystallography administers, documents and provides software resources for these data exchange standards is also described.