Herbs are plants that are appreciated for their flavor, scent, medicinal and food. Herbs are used in cooking as well as in some traditional forms of medicine. In American English, the "h" is silent, while in British English, it is pronounced.
Spices are seeds, fruits, bark, root or any other parts of plants, trees or shrubs that are appreciated for their flavor, color or taste. The difference between herbs and spices is that herbs are the leafy, green parts of plants, whereas spices are from any other parts.