Sativa and Indica are two different types of weed. You can have a plant that is either 100% indica or sativa or any mixture of the two. Sativa plants are known to mostly give someone a "body high" where as indica usually is associated with head or mind-intensive highs. Neither describe quality or strength.

Salvia is a legal plant that can be found at many headshops and online sellers. It produces a hallucinogenic trip when smoked. Be careful though, it can have just as bad effects as good ones for many people.