In most mammals, fertilization occurs internally, within the female's body. This is in contrast to many other animals, such as fish, which release eggs and sperm into the water, where fertilization occurs externally.
After fertilization, the fertilized egg develops into an embryo and then a fetus. The fetus grows inside the mother's uterus, where it is protected and nourished. The mother's body provides the fetus with oxygen and nutrients, and removes waste products.
When the fetus is fully developed, it is born through the mother's vagina. This process is called parturition. After birth, the mother typically feeds the baby with milk from her mammary glands.
This reproductive strategy is beneficial for mammals because it provides a protected environment for the developing fetus and ensures that the baby is born with a ready-made food source.