Every type of pool - whether indoor or outdoor - requires cleaning for the reasons already mentioned. Some actions are needed to be taken more frequently than others, such as removing debris floating on the water's surface. It's important to skim leaves and other matter from the water often so that particles don't sink to the bottom, making it harder for the debris to be removed.
Cleaning the surface is usually a daily chore, whereas vacuuming the sides and bottom of the pool can be done once per week. Other weekly maintenance activities include cleaning the pump, skimmer, and filters. Whenever the pool is occupied, make sure the ground, steps, and diving board are clean.
Removing dirt or grease can sometimes be challenging, but using certain brushes and sponges can help make the work easier. White vinegar is a reliable solution for removing the most resistant grease. Skimming, brushing or vacuuming your pool at least once a week will keep the pool clean. To keep your pool free of debris when it's not in use, invest in a tarp that covers the pool.
Some homeowners use an automatic pool cleaner, which is a robotic machine that can be programmed to clean or detect certain areas where debris exists. These modern machines are effective to a degree but you'll likely need to supplement the cleaning with manual work for best results. If you're using a pool vacuum, make sure it's equipped with all the necessary parts including a vacuum head, telescopic pole, hose, skim-vac, and scrub brush.