osmanthus is a small yellow flower from china. it's very fragrant and has a strong sweet, rich, smell and flavour. it is used like jasmine flowers to scent tea. during the drying phase, it's laid in with the tea leaves, and they absorb it's scent.
i have never seen it sold as a tea by itself. sometimes it's included with the tea. you will see small yellow dried flowers with the leaves.
it's a wonderful flavour, and i definately suggest trying it if you haven't. jasmine tea is good, but osmanthus tea is much stronger, richer, and sweeter of a flavour.
hope that helps,