Almost all horses have leg markings of some sort, from a tiny spot of white to whole white legs. Here are the general definitions of each marking (which are a bit more definitive than markings on the face because they are based on leg anatomy.
This is the smallest of the leg markings & shows the least amount of white. The mark is only displayed around the coronet band, generally rising no more than an inch up from the hoof.
Often difficult to distinguish from the coronet marking, the pastern takes up where it leaves off. The white mark extends more than an inch above the hoof over the pastern but stops at or below the fetlock joint.
Taking up where the pastern leaves off, the fetlock white marking extends up over the fetlock joint up onto the cannon area.
The sock white marking extends beyond the fetlock but doesn’t reach above the knee or hock of the animal.
Perhaps the flashiest & definitely the largest of the white markings. Stockings extend above the knee or hock & can bleed onto the flank or belly.
Some animals have no white on their legs, although some bay animals will have black socks similar to (or in addition to) white ones.
Ermine spots are tiny spots of the coat color that show up on a white marking near the coronet band just above the hoof.