The placenta is an organ made for pregnancy that attaches to the wall of your internal genitalia/uterus and transfers nourishment and waste back and forth from your bloodstream to your baby. Following birth, you'll expel the placenta and the membranes (bag of waters) usually within a half hour. Placentas weigh about 10% of a baby's weight and typically come out easily.
Talk to your health care provider about their approach to your care and your placenta. They'll discuss with you the option of having medication and other treatments shortly after the birth that may help your placenta come out more quickly and reduce bleeding.
Many cultures celebrate the placenta by planting it in a spot special to your family or by using it in other ways. If you opt for this, it's important to remember the placenta is a blood product and to keep it safe from spoiling or spreading disease. At hospital births, placentas are disposed of along with other hospital waste unless you specify that you want to keep it.
See the links below on various approaches to giving birth to your placenta and options for it afterwards.