Oregano is similar to marjoram, indeed sometimes called Wild Marjoram. Oregano is the quintessential flavour of the Mediterranean, especially Italian, cuisine, because of its love affair with tomatoes. European oregano differs from Mexican oregano, but can be substituted.
Oregano herb can be used fresh or dried. The leaves are rounded, tear-shaped and dark green in colour and slightly hairy; the leaves grow to about 3 cm long and covered in a fine down of hairs.
Oregano is less sophisticated than marjoram in flavour, with a strong and robust grassy flavour with some peppery oily warmth. There is also a some bitterness and sometimes a hint of lemoniness.
Oregano works well with tomatoes, just like basil. Because of this affinity to tomato, the mixture of basil and oregano have pretty much become the universal base flavours for pizza and pasta. Oregano also works well with aubergine or eggplant, courgette and sweet peppers, so you will find its use in moussaka, for example. Beef, lamb and pork also enjoy being rubbed with olive oil then some oregano, garlic and a smidgeon of freshly ground pepper before cooking.