Does anyone know what gives plants such as lavender their scent?

I am writing an assignement on the internal and external structures of plants and how they relate to our recreational use, I'd like to write about the physiology that gives a specific plant it's scent,but if you know another recreational use of plants please give me your ideas,i need to be abble to research it though, thankyou

Does anyone know what gives plants such as lavender their scent?
All I know is when the essential oil is extracted from the plant, through steam dissilation or otherwise, it leaves a potent smelling oil that is very strong in use for recreational and medicinal purposes.

Vitamin C Benefits