Algae are currently used in many areas, including dietetics, pharmacy, cosmetology and to increase the nutritional value of food and animal feed due to their chemical composition. They are a source of extremely valuable molecules, including polyunsaturated fatty acids and pigments. Algae are also a valuable source of protein and almost all essential vitamins. They are rich in pigments such as chlorophyll, carotenoids and phycobiliproteins. These substances have a wide range of commercial applications. Due to its very intensive use, the demand for this plant raw material is constantly growing. Therefore, the methods of growing and harvesting algae are constantly improved in order to maximize the cultivation effect while minimizing costs and energy inputs. Future research should focus on improving algae cultivation and harvesting systems, with an emphasis on the possibility of genetic modifications that would allow even more efficient algae cultivation. This review summarizes methods of micro- and macroalgae cultivation, the chemical composition of selected algae species, which are important from the pharmaceutical, dietary and cosmetic points of view and therapeutic and dietary applications of compounds derived from different algae species. The key conclusion drawn from this article is that algae are an extremely valuable raw material, rich in numerous macro- and micronutrients necessary for humans, the acquisition of which is part of the currently important strategy of ecological policy for obtaining raw materials for various industries.