Pergolas were originally long trellises with a lattice worktop that could be used to train up vines. In the backyard, they are often used as an extended trellis over which vines of various kinds can be trained. They come in a variety of styles, but the most common one has an oriental feel to it. A sturdy pergola can have hanging baskets of plants suspended inside it as well as vines growing over it. With good vine cover, they tend to be a little cooler than a fabric covers or solidly roofed gazebo or canopy.