In common parlance, the word "fruit" normally refers to a sweet-tasting, edible plant organ.
What is a fruit?
In botany, a fruit is a plant organ that develops following the fertilization by pollination of one or more ovules, contained in a pistil. Each of the ovules fertilized by a grain of pollen will become a seed. The rounded part of the pistil, which contains the ovules (also called the ovary), will become a fruit.
A fruit is therefore a fleshy or dry organ containing one or multiple seeds. Once matured, it serves to propagate the species.
Berry or drupe?
In drupes, the inner part of the ovary, called the endocarp, is thick and hard, forming a tought, stony pit around the seed.
In berries, on the other hand, the endocarp forms a thin, flexible envelope around the seed. The consumption of berries and drupes by animals allows their seeds and pips to be spread around. They are not harmed by the animal's digestion and are excreted a short distance away.