A brownie is a squarish, flat cake dessert. It is a mixture of cake and cookies and comes in different shapes and sizes, mostly in a square shape.
They usually have a heavy texture, and might include nuts, chocolate fudge, or chocolate chips. Brownies are meant to be eaten by hand, and accompanied with a warm drink, normally tea, coffee, or warm milk.
They are found only in coffee shops (cafes) and restaurants. In restaurants, they are always served as desserts.
Here are some pictures of brownies: