In Mandarin Chinese, 入 (Pinyin: rù) is a verb meaning “to enter”, “to go into”, “to arrive” and so on. Careful: in some dialects, it also means “to have sexual intercourse”.
According to Wiktionary, this hanzi represents “an arrowhead indicating ‘to enter’”, while Uncle Hanzi explains it as “an open tent door”. The latter explanation is easier to remember and clearly more inviting.
Combining 入 with 口, we get 入口 (rùkǒu🔊), a useful word that means “entrance”, “way in”. I find both characters quite erotic.