Greek or Mediterranean oregano, like many herbs, comes from the mint family. Mediterranean oregano is very closely related to marjoram and is similar in appearance; in fact, oregano means marjoram in Spanish.
Oregano and marjoram are in fact two different herbs and possess different flavor characteristics. Oregano has a milder, sweet aroma and flavor that matches well with thyme, basil, rosemary, sage and marjoram itself. It is used extensively in Italian cooking and is often found in pizza, pasta sauces and many other tomato based sauces.