Oregano is known around the world as the pizza herb. Its distinctive fragrance is an important part of what gives pizza its unique, delicious smell, but oregano is also a popular ingredient on its own merits. It frequently appears in Mexican and Mediterranean recipes, though, like most herbs, it can be used to boost the flavor of just about any meal.
Despite its sweet smell and pungent flavor, oregano is easily substituted. Marjoram (an herb that oregano is often mistaken for) is ideal, as their tastes are very similar. However, if you're out of marjoram, sage, parsley, basil or thyme will also do the trick.