digitigrade
A non-human character who walks on their toes rather than the sole of their foot. In real life, many animals are digitigrade, including cats, dogs, and foxes.
This tag primarily refers to humanoid (furry, monster girl, kemonomimi, taur) characters that have a digitigrade body structure, as well as some monsters. This tag also includes a similar hooved leg structure known as "unguligrade", where an animal walks on the tips of their hooves.
Sometimes called "reverse-jointed", as digitigrade legs can look like they have a "knee" that bends the opposite way to a human knee. However this "knee" is in fact the heel; the actual knee may not be immediately apparent.