A gazebo is a freestanding, outdoor room with a roof. It is often round or multi-sided, but could be square. The angles of complex, multi-sided gazebos can be difficult to perfect. Sometimes it is best to purchase a pre-engineered structured if it suits the style of your landscape design. There are some elaborate and attractive products available.
The most pleasant thing about a gazebo or a pavilion is protection from the elements. It is sometimes called a summerhouse. Gazebos and pavilions make good housing for outdoor kitchens and help protect furniture cushions and equipment. They can provide storage for pool equipment and tools. A connection to water, electricity, and a digital network make the structure even better. Incorporating a stone fireplace or heating element can extend its use and stretch out the outdoor living season. Walpole Outdoors is a company that has been making beautiful outdoor structures for decades. I recommend visiting their site for examples of how well-built outdoor structures should look.