If the entire fruit is fleshy, except for maybe a thin skin, we call the fruit a berry. A berry might contain one seed or many. Grapes, avocados, and blueberries are berries. They all have a thin skin, but most of the fruit is fleshy. Though don't get confused by the name of fruits like Strawberries, when actually, are actually "not" berries, because the seeds are on the outside: on a real berry, the seed or seeds must be inside. 