Prop is a term commonly used by the holiday lighting industry that is a mold that supports the outline of pixel lights used in creating or enhancing the desired effect. Props are used for just about anything, from outlining your house to full animated props. The propls can be on your house, a display in the yard, corrugated plastic, and so on.
There are so many light props to choose from. From purchased props to DIY, there's bound to be something for everyone. The advantage of pre-made "Coro", or Coroplast based plastic. Its like cardboard but plastic-based. It's waterproof and weather-resistant, as with most plastic items, it's no UV proof.