The authors of the book are forest engineers from Bulgaria with a huge experience in forest ecology researches and study of the influence of the forest on economy. The research aims to present the ecological, social and economic functions of forests. It consists of 3 parts: the first part presents the peculiarities of forest ecosystems, contemporary concepts of forest ecology, kinds of forest resources and their relation to development and survival of society, general and specific functions of forests, specificity of forest ecosystems in comparison with other ecosystems in the biosphere. In the second part of the paper there are presented economic functions and importance of forests and influence of forests in the development of agriculture. The last, but not the least part of the book presents the ecological function and role of the forests. Certainly, - some conclusions were also made.