If your bird isn't going to be brooding the egg, I'd be tempted to open it and see if there were any other abnormalities.
Birds do lay some very strange eggs. Wind eggs are one that really surprise people when they find one, as they are like a regular egg, with yolk, albumin, and the membrane around it, but no calcium shell. It is soft and squishy. It's kind of perplexing as to WHY they lay these, as they may lay one like that with all others being normal,a nd then never do it again.
I also had one hen try and lay an egg twice normal size (she eggbound and we had to put her under isoflurene gas to relax her enough to manipulate it out), which was closely followed by the tiniest little egg about the size of a small Budgie egg.
Some of them have no yolk, some have double yolks. The worst are the ones with the thickened, rough shells that are due to calcium and vitamin D imbalances (nearly as anyone can figure out) that result in egg binding and are very hard to get free.
Sweet apples, as was guessed, are the dessert apple catagory that are sweeter to the palate, and are usually eaten raw, as opposed to the tarter, cooking variety apples, or even the very tart cider apples.
Dessert apples would cover things like Yellow Delicious, Gala, Orange Pippins, Lady apples, Honeycrisp, or Fuji.
All purpose are more like Macintosh, Jonathan, Winesap,Granny Smith,etc.
Cider apples are not usually sold in stores and are often unnamed varieties as well as a few named ones.
Then there are also Crab apples, most of which are not very palatable fresh to downright horrid; and even pickled and sweetened, only a few, like Dolgo, make anything edible.