Thigh-high boots are footwear that ends above the knee. They usually cling to the calves of the wearer, highlighting their silhouette. Since they also tend to be paired with shorts or a short skirt, they can also be used to showcase the zettai ryoiki (絶対領域, lit. “absolute territory”) of the thighs, which is common in anime-style character designs.
The idol Hatsune Miku is almost always spotted with her thigh-highs! Do you recognize any of the other gorgeous characters pictured below?