Got a flat butt, want to make it pop? We all love the butt and we all should love our own. There are three main muscles that comprise the butt, the gluteus maximus, gluteus medius, and the gluteus minimus. The gluteus maximus is the largest of the gluteal group. Its origin is the posterior line of the upper ilium, the posterior surface of the lower sacrum, and the side of the coccyx. Its insertion is two-fold: First, the lower and larger portion of the gluteus maximus end with a thick tendon that passes through the greater trochanter (hip) into the iliotibial band. And there is also the gluteal tuberosity between the vastus lateralis (a quadriceps muscle) and adductor magnus.
The gluteus medius (G-med, pictured right) originates on the outer surface of the ilium above and in front of the anterior gluteal line. It also originates at the gluteal aponeurosis. The insertion of the G-med converges on a tendon that attaches to the lateral surface of the greater trochanter (your hip joint). Ultimately, the G-med tendon inserts into an oblique ridge that runs down and to the front of the lateral surface of the greater trochanter.
The gluteus minimus (G-min) originates in front from the outer surface of the ilium between the anterior and inferior gluteal lines. In back, it originates from the margin of the greater sciatic notch. It inserts on the deep surface of a radiated aponeurosis via a tendon that attaches to the anterior border of the greater trochanter. The G-med and G-min perform similar functions, depending on the position of the knee and hip joints. With the knee extended, they abduct the thigh (out to the side away from the opposite leg). When running, they stabilize the leg during the single-support phase. With the hips flexed, they internally rotate the thigh. With the hips extended, they externally rotate the thigh.
Here is a video on some exercises you can do to work that fanny, butt, booty, ass, or bum or whatever you call it.