What is the difference between calluses or corns?

Similar : Both corns and calluses are thickened skin due to pressure and are similar. Calluses are generally on the bottom if the foot in areas of pressure. Corns are usually on the top of, or between, the toes. They are smaller, deeper, and painful.

Location: When the lesions happen on top of the toes these are corns. Calluses happen on the bottom of feet. Both are thickend skin.

Not much.: Neither term is a technical term. "corns" are usually what people call the soft calluses that develop on toes, while "calluses" usually refer to the thick skin on the sole of the foot. This thick skin can be diffuse and wide-spread, or have a core or nucleus to it. All usually occur due to pressure or friction; very occasionally trauma or a plugged sweat gland can be a component.