指甲 covers both fingernails and toenails (脚趾甲 jiǎozhǐjia is the specific term for toenails). 指甲油 = nail polish. 指甲刀 = nail clipper.
culture
In ancient China, long fingernails (especially on the pinky) signaled wealth and status - proof that one didn't do manual labor. Some people still grow a long pinky nail today.
