Also known as leg wraps, they are long strips of cloth wrapped around each leg. They were used most notably by soldiers from various powers in the late 19th and early 20th centuries, but also by ancient civilisations in place of elastic socks.
Puttees are not to be confused with gaiters, in that gaiters are specialised garments which do not require to be wrapped repeatedly around the leg to provide protection, instead they are usually secured via a system of straps and buckles.