Corns and warts are formations of hard skin that can look very similar, however it is important to diagnose it correctly as they both have different causes and treatments.
Corns form due to pressure and forces in the area from walking or running for long periods of time, or wearing tight shoewear that causes rubbing. They commonly appear in high pressure areas such as the toes or balls of the feet. Treatment for corns include cutting them out and offloading the area.
Warts are viral infections caused by a strain of the Human Papilloma Virus which invades healthy tissue. These can present anywhere in the feet, and can appear in clusters. These form due to cross infection, from walking on unhygienic surfaces such as shared change rooms or swimming pools. Also having a weak or underdeveloped immune system can cause increased vulnerability. This is why warts are commonly found in children and those taking immune suppressants in chemotherapy. Conservative treatment for warts include salicylic acid or liquid nitrogen to burn the wart cells, or surgical removal if this has not worked.