What exactly is a seed?
A seed is the structure produced from a fertilized ovule. It comprises a protective coating (seed coat) that encloses an embryo and a food supply.
What is a stone?
The stone is the hard layer (hardened endocarp) around the seed of drupes (peach, plum, cherry, olive, apricot), a type of fleshy fruits. A drupe usually contains a single seed.