问 (traditional 問) = 门 (door) + 口 (mouth) — a beautiful little scene: a mouth at the door, asking to be let in, asking after the household. To ASK, to inquire.
问 is 'to ask': 问你 (ask you, with 你), 请问 (qǐngwèn, 'may I ask…' — the polite opener for any question to a stranger: 请问，洗手间在哪里?). It also means to send regards: 问好 (with 好) — '请帮我问他好' = 'please give him my regards'. And 问题 (wèntí) is 'a question / a problem'. From a mouth at the door, 问 became the character of curiosity and courtesy.
A mouth (口) at the door (门) — to ASK.
请问 ('may I ask') is the polite way to open any question to a stranger: 请问，洗手间在哪里? ('Excuse me, where's the restroom?'). 问好 means to send someone your regards.