What is the difference between a berry and a fruit?

There is no difference, berries are a type of fruit.

Berry:

It is a soft, juicy, fleshy fruit that develops from the ovary or in association with other floral organs. There are many types of berry fruit trees, such as grapes, kiwi, raspberries, currants, lingonberries, fruit mulberry, figs, pomegranates, poppies, heart fruit, papaya, guava, pawpaw, blueberries, and passion fruit.

Fruit:

It is the edible fruit of a plant that is juicy and has a predominantly sweet and sour taste.

Expanded Information

Berries are mainly categorized in fruit classification:

Grape family:

Grapes, raisins, currants, black currants, red currants, and others.

Rhododendron family:

Blueberries, cranberries, lingonberries, umeboshi, etc.

Cactaceae:

Dragon fruit, yellow dragon fruit, red dragon fruit, cactus fruit, etc.

Edelweiss family:

Yangtao, three astringent fruits, etc.