Agroforestry is probably one of the most controversial word for the definition of a combination, or integration of trees (forestry components) and crops or fodder (agricultural components) into various types of cropping systems. Agroforestry systems varies from the most simple (SAF), a crop associated with a tree, to the most complex in terms of structure, the CAF (complex agroforestry systems) with multi-strata components, a large biodiversity in terms of species and frequencies, where several perennial crops and trees are associated. After describing rapidly the concept of agroforestry, we will focus on a particular typology and provide two examples of simple agroforest (SAF), parkland in Africa, and complex agroforests (CAF) in Indonesia. SAF are considered as a “regreening factor” when CAF in humid tropics can be considered as a reforestation factor. CAF in humid tropics are developed by farmers, whose structure and dynamic are close those of secondary forests. Such CAF may replace natural forests in areas where forests may have completely disappeared. There is therefore a clear dynamic from forests to agroforests, from natural vegetation to real man-made forest-like cropping systems based on trees.