Breast augmentation is done to increase the size of the breast. This will also lift the breast somewhat, because as the tissue envelope of the breast fills, it becomes somewhat higher. However the amount of lift is limited. If your breasts are both smaller than desired, and ptotic it may be necessary to do both an augmentation to increase the size, and a mastopexy to tighten the skin. This is called an augmentation mastopexy. (Mastopexy is discussed in more detail in the next section).
Placing the implant under the muscle gives a thicker covering over the implant, which can make the implant less noticeable, and may also decrease the risk of capsular contracture. The down side is that when you move your muscles, it can compress the implant, which can cause movement to the breast, which may look unnatural. The sub-glandular position will prevent the breast from moving when you flex your chest muscles, but it decreases the amount of covering over the implant, which may make it more visible. It may also increase the risk of capsular contracture.
Breast Augmentation is usually done by placing a silicone implant underneath the breast tissue in one of two positions. The implant can be placed under the breast tissue but over the muscle, in what is called a sub-glandular position (picture in the center). The other option is to place the implant under the muscle in what is called a sub-muscular position (picture on the right).