A normal human has two kidneys, although it is possible to survive with one. The kidneys are bean-shaped and located approximately mid-way on the upper torso on either side.
Kidneys are often compared to filters for the human body. They have a variety of functions, but the most important is to filter out organic waste from blood and the byproducts of metabolism. The kidneys are able to dispose of waste products, like urea, through two ureters (one for each kidney), which is then directed to the bladder to be expelled. The kidneys also remove any excess electrolytes to maintain an appropriate balance in the body.