I'm sorry for the dumb question but could someone explain what a Decoy is?

From James Thompson, Project Admin and scientist:

decoy - a decoy is also a model for a given protein (or RNA). This term came about during the early days of energy function design, when people first started writing energy functions to discriminate between "native" structures, which are correct structures solved by experimental methods, and "decoy" structures, which are computationally created structures that are incorrect to some degree. I found the term to be odd when I first encountered it as well, but I've since grown accustomed to it. In most contexts, model and decoy can be used interchangeably.