Despite what the name implies, 4-season tents are intended primarily for winter or high alpine use. 4-season tents have fewer mesh panels, heavier fabrics, and sturdier support systems than 3-season tents in order to withstand harsh winds and intense storms. They also have rounded dome designs that prevent snow from accumulating on the roof and causing a collapse. These tents can still be used any time of the year, but they are heavier and feel stuffier in warm weather, so if you camp primarily in the warmer months, stick with a 3-season tent.
Preferred by alpine climbers who are more worried about shedding snow than rain, single-wall tents are constructed with waterproof/breathable fabrics such as Gore-Tex to eliminate the need for a rain fly. Double-wall tents consist of an fly over the tent body—this tent style is more common in 3-season tents.
4-season tents sleep anywhere from a single person to eight or more. Often, these tents offer more floor space to accommodate for the added gear necessary for cold-weather camping.