Ricotta is a term that refers to a dairy product rather than a real cheese. It can be fresh or cured, sweet or salty, and even slightly spicy. It is produced in many regions of Italy, with different flavours and textures.
It is prepared with whey - cow's or sheep's milk - which is cooked twice (thus its name, "ricotta" in Italian literally means double cooked) until it turns into small cottage cheese. This is collected and pressed in wicker baskets covered with gauze and left to drain for 12-14 hours; afterwards the ricotta can be sold on the market. The one prepared with sheep's milk is tastier and more substantial than that of cow, which is leaner and thus more digestible.
Ricotta is an excellent ingredient for making cakes, both savory and sweet; it goes well with tomato sauce to season pasta and it is perfect to stuff ravioli or tortellini. Fresh ricotta has a very soft texture (it can also be eaten naturally), while the aged one is harder and can also be grated.