There are three basic types of pools.
The Standard: This style pool has a uniform square or rectangular shape. Generally 20 feet x 40 feet, the bottom of the pool is typically 3-6 feet deep, and can be one uniform depth, or have a sloping pitch. This pool style can be much cheaper then a Complex Custom Pool.
Complex Custom Pool: This is a more expensive solution, but this type of pool can be built to accommodate the subtleties of your back yard, and allows for additional integrated water features. Attached spas, coves, and non-symmetrical shapes can be created. These types of pools take longer to build, and typically require greater maintenance as well.
Lap Pools: This is a nice reasonably priced solution that allows you to cool off on a hot summer day and get your daily exercise. Lap pools are typically 11 foot x 40 foot, with a level depth of 5 feet.