Here's some links to help you if you're new to the world of medicinal herbs

Medicinal HerbFaq (part 1) From Henriette Kress
Medicinal HerbFaq (part 2) From Henriette Kress
Medicinal HerbFaq (part 3) From Henriette Kress
Medicinal HerbFaq (part 4) From Henriette Kress
Medicinal HerbFaq (part 5) From Henriette Kress
Medicinal HerbFaq (part 6) From Henriette Kress
Medicinal HerbFaq (part 7) From Her Again