Translation:Is it bright outside?
The meaning of the single Kanji 明 is "bright" and "light".
It is also a word in itself read as めい meaning "brightness". It can also refer to some other words, but those are either archaic or very specific (like the Buddhist term みょう meaning vidya aka wisdom).
It consists of the Kanji for sun/day 日 and the one for moon/month 月
You can use dictionaries like jisho.org or the Takoboto app to easily look up Kanji.