Lilac or Syringa spp. (the common species is vulgaris) is in the olive family and is native to the Balkan Peninsula in Southeastern Europe. People emigrating from Europe brought the shrub to plant in their gardens in order to savor a piece of home. Here out west pioneers brought lilacs with them during the 1800’s and now you may find lilac that grows nearly wild in abandoned lots and homesteads.
Lilac fragrance is wonderfully intoxicating however it is very difficult to capture the scent and only until recently is there even a true essential oil made from the flowers.
The flowers are edible and have some medicinal qualities. I have to say eating even a single flower raw is a flavor exploding experience with slight astringency (drying to tissues), almost bitter, and very floral. I would say these are best for garnishes and edible flower displays on pastries rather than whole meals.
Medicinal uses are still a gray area when it comes to just the flower. Most resources that I have found (random blogs, pfaf.org, A Modern Herbal) list that the medicinal benefits of Lilac come from the leaves and fruit. Apparently used as a tea or infusion historically it has been used as a anti-periodic. Anti-periodic basically means that it stops the recurrence of disease such as malaria. There has been some studies that indicate a febrifuge action which may help bring down fever.