That is a picture of the Latissimus Dorsi. This muscle is what give bodybuilders their 'wings' and width. The latissimus dorsi is a triangular, flat muscle, which covers the lumbar region and the lower half of the thoracic region. This makes up some of the armpit and stretches down near the glutes.
Rhomboids
This is the middle back. The rhomboids are found on the spinal column and they attach to the middle of the shoulder blade. The rhomboids are used to bring the shoulder blades together.
There are also a whole bunch of little muscles in the back which run along your spine.
-Erector spinae- group of muscles that are in and support the spine as well as extend the spine.
Trapezius (Traps)
Another powerful muscle of the back is the trapezius. The traps run all the way down the upper section of the spinal cord and attaches at the middle of your back. Functions- shoulder blade movement and shrugging.
Lower Back (Lower Trapezius)
This is the continuation of the Trapezius as mentioned above.
Mass building exercises for above:
Chin Ups
Wide, Middle Lat pulldown
Dumbbell Rows
Reverse, Snatch Grip Deadlifts
Dumbbell Rows
Bent Over Barbell Rows
Seated Rows
Behind The Neck Press
Hyperextensions
Straight Arm Pulldown
