Several parts combine into one character.

Phonetic-semantic compound: 月 (the flesh-radical, identical in shape to "moon" but historically 肉, body — already discussed in 月 entry) + 几 (a small table / armrest, providing phonetic value). The encoded meaning: "soft flesh / fine skin texture" — the smooth surface of the body. Identical across 繁體 / 新字体 / 简体.

Cross-language usage split is sharp on this character: — Korean / Mandarin: 肌 is mostly literary or technical. The everyday word for "skin" is 皮 (Korean: 피부 = 皮膚). Mandarin uses 肌 mainly in 肌肉 (jīròu, muscle). — Japanese: はだ (hada, skin) — the kun-reading — is the EVERYDAY word for skin, especially in cosmetics, health, and beauty contexts. お肌 (ohada, "your skin") appears constantly in Japanese commercials.

Mandarin: jī, level 1st tone. 肌肉 (jīròu, muscle), 肌肤 (jīfū, skin / complexion — formal), 心肌梗塞 (xīnjī gěngsè, heart attack — "heart-muscle blockage" — modern medical vocabulary). Note 肌 in Mandarin tends to mean "muscle" as much as "skin" — slightly different from Japanese where 肌 strictly means skin.

Japanese: kun-reading はだ (hada) is dominant — 肌 (hada, skin), お肌 (ohada, your skin — polite), 肌色 (hadairo, skin color — note this term is being phased out for ペールオレンジ "pale orange" in inclusive contexts), 肌着 (hadagi, undergarment — clothing worn against skin), 鳥肌 (torihada, goosebumps — "bird skin"). 鳥肌が立つ (torihada ga tatsu, "goosebumps stand up") describes shivers from awe or chill.

The Japanese cosmetics industry is built on this character. Walk through any drugstore cosmetics aisle in Japan and you'll see 肌 in 90% of the product names: 美肌 (bihada, beautiful skin), 素肌 (suhada, bare skin), 乾燥肌 (kansōhada, dry skin).

Memory aid: flesh + smooth surface = the soft skin that covers us.