Forest Gardens are sustainable, minimal maintenance agronomic systems, that grow a combination of trees, shrubs and perennial plants, often for great yields. The system considers the vertical space as much as horizontal, meaning a greater yield per sq of land, because produce is created in the earth, on the ground and above the ground (specified in 7 layers). The primary aims of a forest garden are sustainability and climate fluctuation endurance, production and low maintenance. The crops which are produced will often include fruits, nuts, edible leaves, spices, medicinal plant products, poles, fibers for tying, basketry materials, honey, fuelwood, fodder, mulches, game and sap products. The key features contributing to sustainability, are devised from the characters of species used at each level, each are chosen so their properties benefit the surrounding species. Plants that increase fertility such as nitrogen fixers, deep rooting plants that tap into mineral resources, plants that attract pest predators, varieties offering disease resistance, trees that offer shade from harmful sun exposure and leaf litter which improves nutrient cycling and drought resistance, are all examples of how species characteristics work in harmony for the forest garden. In cases of large lands and particular produce, forest gardens are used as land dividers as oppose to typical low produce hedges.
For more info, see https://www.agroforestry.co.uk/about-agroforestry/forest-gardening/