What is it? Good question my child. You see Wizards of the Coast had a magazine called Dragon that released material for whatever the current version of D&D was out. This was a hard back redited version of some of those magazines. You know kinda like unearthed arcana for 5e. But Wizards would release other material besides just the magazine's material in hardback.
D&D Dragon Magazine Annual
Daniel Cadded October 12, 2019