Compression uses elastic support fabrics to hold breasts closer to the body. Reduces the amount of bounce, but may produce a “uniboob” appearance which some women object to.
Encapsulation is another method of reducing bounce, encapsulation typically uses molded, often semi-rigid cups to contain the breasts. The shape of the cup, and the way it's built into the bra, limits movement of the breasts.
Many bras use a combination of compression and encapsulation to support breasts.
Underwire/frame support system
Stiffening components underneath the breast hold it up and provide shaping. May also contribute to the overall support of the bra.
Straps support the weight of the breasts by cantilevering it off the shoulders, much like a suspension bridge. Larger breasts require broader, non-stretchy straps.
Many A/B bras are designed to pull over the breasts. When there's a lot of difference between band size and bust size, it's difficult to pull on a bra that's suitably sized in the band, so most C/D/DD bras have a front or rear closure. To prevent chafing, the closure should be covered so that it's invisible to the skin.
For more information see our Sports Bra Sizing Guide