This term actually isn't new—according to Mirriam Webster, the first known use of "vibe" was 1967. Dictionary.com says that the association between "vibrations" and a source of positive energy goes back to 1983. In the '60s, the term "good vibes" was popular (as evidenced by the 1966 Beach Boys song "Good Vibrations").

The word "vibe," as opposed to "vibes" or "vibrations," is used commonly today. If we want to get technical, "vibe" can be used as both a noun and a verb. When it's a noun, "vibe" describes the distinct emotional impression of a place, gathering, or even a person. It's the feeling you get after you leave, and you're reflecting (i.e. "that place had a spectacular vibe" or "this room has a weird vibe"). When a verb, "vibe" means to kick back and hang out, or to get along (i.e. "she and I were vibing on our date").

Or, you can say, "It's a vibe," referring to the specific emotional atmosphere or sensation you find yourself in.