What could activate my car alarm?

I drive an Acura TSX. Today, while the car was in my driveway, the alarm went off. I've never had the alarm go off on my car before. Is there anything that could cause the alarm to go off on its own? I am hoping that the alarm doesn't mean that someone was trying to break into my car while it was in front of my house, so I'm looking to all other options. Ideas?