A baby bottle is a bottle with a teat (also called a nipple in the US) to drink directly from. It is typically used by infants and young children when a mother does not breastfeed, or if someone cannot (as conveniently) drink from a cup, for feeding oneself or being fed.
In particular it is used to feed infant formula, expressed breast milk or pediatric electrolyte solution.
Source:
http://en.wikipedia.org/wiki/Baby_bottle
