Marjoram is an herb. People make medicine from the flowers, leaves, and oil.
Marjoram is commonly used for runny nose, cough, common cold, other infections, and various digestion problems, but there is no good scientific evidence to support any use.
In foods, marjoram herb and oil are used as flavorings. In manufacturing, the oil is used as a fragrance in soaps, cosmetics, lotions, and perfumes.
Don't confuse marjoram with oregano (Origanum vulgare), which is also referred to as winter marjoram or wild marjoram.