So people may not know what an elevator pitch is. But it's a pitch when you only have a short amount of time to get someone's attention and to pitch them your client. They use the analogy of being stuck in an elevator, because you have their attention for however many floors you have them in the elevator.
An elevator pitch doesn't necessarily have to happen in an elevator. It can happen at a dinner party or at a cocktail party where you're introduced to somebody, and you have a quick amount of time. You know that this is the person you've been trying to reach, and you need to have a short, under-a-minute pitch on whatever it is you're promoting.
What makes a successful elevator pitch is definitely keeping it short and sweet. Again, definitely being witty and charismatic. It's getting to the point and again, knowing your audience; knowing that person you're pitching to, what they want to hear, and always having a business card so they can follow up with you.