A pergola is a structure that could very well serve as the roof of a patio, but can also be free standing. It is a type of gazebo, but it looks rather peculiar. It's open on all sides, and most pergolas also have semi-open or lattice-patterned roofs.
A pergola is essentially an open terrace. If the name did not give it away, it is Italian in origin, and many pergolas can be seen throughout Italy, where such outdoor structures become meeting places for friends, families and parties. When vines are trained on it, the vines can grow and climb along the pergola nicely and provide the shade that the lattice-patterned roof cannot. A row of pergolas positioned one after the other with wisteria, grapevines, or other lush, woody vines trained upon them creates a peaceful covered walkway from one place to the next.
If you so chose, a pergola can be the centerpiece of your backyard. Since there are no walls and not much of a roof either, a pergola puts you both inside and outside at the same time. You have the feeling of being indoors since there's a structure above you, but since the structure allows the elements in, it's much like being outside as well. It can define an outdoor living space without unnecessarily constraining it. Not only is a pergola very low-maintenance, but the structure also creates a very relaxing environment that is conducive for backyard entertaining. Maybe that's why they're so popular in Italy.
Building a stone walkway to your pergola adds a nice touch to your backyard as well, and it lets your guests know that the pergola is the main attraction, and that's where the entertainment is. While a pergola is an odd structure, its unique purpose-blending the inside and outside together-makes it remarkably different from an ordinary patio or even a free standing gazebo.