'Castile soap' technically refers to a traditional soap that is made from only olive oil and lye in solid form and is from Spain. Nowadays, it describes a natural liquid soap of a variety of base oils thanks to Dr. Bronner's. It can be used for almost any cleaning purpose: wash the car, dishes, brush teeth, laundry soap, shampoo, body & hand wash, floors, an ingredient in your homemade spray cleaner, etc. It is quite liquidy, though, so be aware it serves some purposes better than others. This soap comes unscented, but you can add a couple drops of your favorite essential oil.