An arbor or a passageway of columns supporting a roof of trelliswork on which climbing plants are trained to grow. Now that you know what a pergola is, talk to Prellwitz Construction about getting one of your own. Pergolas aren't just a deck on steroids, they serve as functional outdoor spaces that provide shade and plenty of places to hang plants, baskets, lights or wind chimes. Some are even used to train grape wines. A pergola can be attached to the house as shown here, or can be built separately.