A climbing harness is the most essential piece of equipment for the sport. Each person in a climbing team needs one. As long as you are climbing you need one. Safety must be taken whether you are involved in traditional, aid or free climbing. There is a different climbing harness for each activity. In general however, they all have the same idea.
A climbing harness has a waist belt and leg loops. Leg loops are padded and adjustable for extra clothing layers. Both help you climb and descend preventing flipping over falls. A climbing harness has padding on the waist belt for comfort. Those for traditional and multi-purpose climbing, have 2 to 4 belt loops. These are meant for your carabiners and quickdraws gear.
On the other hand, a climbing harness for big wall and aided climbs has multiple 6-10 gear loops. A much thicker and wide belt padding is designed to provide added comfort on multi pitch climbs. A sit harness is a climbing harness with a seat. This allows you to sit more comfortably over the leg loops. This can be a good choice for beginners.
A body climbing harness has leg loops, waist belt and a chest. This full set is usually used on kids as they have a tendency to flip upside down. The full body climbing harness provides body support and stability. It is also used to haul heavy load. As such full body are also used for rescue missions.
A climbing harness is necessary as it also allows your secure attachment to the rope. The belay loop on the harness provides attachments via carabiners while belaying. For safety purposes, allow a 3 in of a tail when you try it on for future adjustments. Your harness should fit comfortably and be easy for you to sit straight. If you feel any tightness try another climbing harness.