The sky energy... once known as a mystical essence that kept us from flying into space. Now we know this is the air. It can also mean atmosphere, though, because that's what a bunch of air between the earth and space is called. ここの空気はいいね！
Figuratively, this can also refer to the mood that's in the air or room, but not a specific person's mood!
This is a jukugo word, which usually means on'yomi readings from the kanji. If you know the readings of your kanji you'll know how to read this as well.
The mountain air is so clean.
Some cool air came in from the outside.
Please just take the hint.