Ambience is the feel of a place — the light, the sound, the smell, the way people move there — and the mood that gives you. A café can have a warm ambience; a hospital waiting room can have a cold one. We use it about rooms, streets, restaurants, and sometimes a whole evening, not usually about a person. It is a little fancy: in casual speech people often just say atmosphere or the vibe. There is another spelling, ambiance, from French. Though actually they are the same word; some writers like ambiance for restaurants and interior design, and ambience for the general idea, but most people mix them and nobody is confused.