个
gè · HSK 1
piece
个 = generic measure word for 'one item' — the default counter in Mandarin
个 (gè) is the most common measure word, used between a number and almost any noun (一个人 = one person). Originally depicted a single bamboo stalk, hence 'one piece/item'. When in doubt, 个 usually works.
个 — person 人 over enclosure-like component (simplified from 個)
个 is the simplified form of 個, originally a measure word for bamboo stalks. The traditional form combines 人 (person) with 固 (firm, phonetic). Over time it became the most common general-purpose measure word in Chinese, used for people and many objects without a specific classifier.