Generally applied to food that's made to look like other food, or at least other objects. It could be as simple as a cake made to look like a television set, or as imaginative as mashed potatoes colored and arranged as an ice cream sundae.
Origins are from Season 16, episode 2 of The Simpsons. Marge enters a baking contest and the other contestants mock her for making "tasty fakes", a dessert made to look like hot dogs from deep fried cookie dough and meringue.
"These sushi cupcakes are so awesome!"
"I know, they're the best tasty fakes I've ever come up with. All they are is bite sized vanilla cupcakes lined with fruit roll up and coconut on top."