There are two main types of lights, these are LED pool lights and fiber optic pool lights Both types have differences in terms of brightness, level of maintenance, ease of changing bulbs, and costs involved. Also when looking at lights you mst decide whether you want a light thats going to light up your whole pool or are you going to get a floating light for aesthetic purposes. There is also the possibility of getting a pool light that runs off renewable energy.
LED lights are fully submerged in the pool and are in a casing so that water does not get in. they are not too difficult to replace and lowering the water level is not needed to change it. You can just bring the housing out of the water and then replace the bulb. It should take around 15 to 30 minutes. Bulbs usually need changing after 7-15 years. Fiber Optic light bulbs are for those people who want to add a nice look to their pool with a lightbulb that changes colour. they are more expensive, due to a fan to cool the bulb and an electric motor to wheel the colours. These are quicker and easier to change the bulbs but they are slightly more expensive.
When choosing the power of your bulb there is 120 volt and 12 vlt, these do not make much of a difference in brightness but is mainly there because some pools are recommended to run on 12 volts for precaution.