The tree or large shrub you're describing that has rounded leaves and edible brown nuts is likely a hazelnut tree (Corylus avellana). Here are some additional details about hazelnut trees:

- Growth: Hazelnut trees can grow up to 25 feet (7.6 m) tall and have multiple stems.

- Leaves: The leaves are usually rounded or oval, with a serrated edge.

- Nuts: Hazelnuts are the fruit of the hazelnut tree and are encased in a hard, brown shell. The edible nuts are sweet and have a slightly nutty flavor.

- Growing conditions: Hazelnut trees grow best in temperate climates with well-drained soil and full sun.

- Uses: Hazelnuts can be eaten fresh, roasted, or used in baking and cooking. They are also used to produce hazelnut oil, which is used in cooking and cosmetics.

Hazelnuts are a delicious and nutritious food source. They are a good source of vitamins and minerals, including vitamin E, magnesium, and manganese. Hazelnuts are also a good source of monounsaturated fats, which can help reduce cholesterol and improve heart health.