Pantyhose are sheer tights, a garment that snugly covers your legs. It was once very common for certain jobs to require women to wear pantyhose.
You might call pantyhose tights or stockings — this word is uncommon outside of the US, and it's typically used for a particularly thin, sheer hosiery with built-in underwear. Pantyhose were invented in the 1960s, replacing old fashioned knee-high stockings that were held in place with garters. The name pantyhose is a combination of panty, undergarment or underwear, and hose, which is short for hosiery.