How Breastfeeding Works
Breastfeeding is the normal way for humans to feed their children. Just like all mammals, we are built to provide our own milk to our babies.
During pregnancy, the areola (the darker part of skin surrounding the nipple) gets even darker - this thought to help provide a target for a baby to help with latching on. The small bumps on the areola are the Montgomery's gland which provide a protective coating for the nipple. The nipple itself has about 20 openings to allow milk flow. When a baby latches on, the baby's mouth creates a vacuum which is when the milk comes out of the nipple. That means that the baby is getting milk when the baby's mouth opens (milk is not squeezed out of the breast).
When the baby first latches on, baby will suck quickly and with less suction, this is to help with the let down of the milk. Once the milk has let down, baby will slow the sucking to a longer, rhymic pattern with more suction. Mom's should be able to hear baby swallow for every couple sucks.
Baby breastfeeding stimulates mom's brain to release more hormones (chemicals). In the first few weeks these chemicals help mom feel more relaxed, help improve attachment and most importantly tell the body to make more milk!
Here are direct links to a few other "How Breastfeeding Works" pages.