Most all apples need a different variety nearby to pollinate. Some very good apples can be grown from seed while others may be less than optimal. The apple trees sold as say a McIntosh are grown from a graft on a root stock. The root stock used determines if it is a dwarf, semi-dwarf or standard. Long story short, the seeds out of a McIntosh apple will grow into a tree, but will not produce McIntosh apples. They will be a hybrid cross between the McIntosh and whatever variety the blossom was pollinated with.