The four types of toilets are flush toilets, pour-flush toilets, pit latrines, and composting toilets. Each type has its own advantages and disadvantages. Flush toilets are the most common type of toilet in the developed world. They are easy to use and require little maintenance. However, they use a lot of water and, if not properly maintained, can become breeding grounds for bacteria and other pathogens. Pour-flush toilets are similar to flush toilets but use less water. They are common in developing countries where water is scarce. However, they can be difficult to use and maintain and, if not properly maintained, can also become breeding grounds for bacteria and other pathogens. Pit latrines are the simplest type of toilet. They consist of a hole in the ground covered with a lid or slab. Pit latrines are easy to construct and require no water. However, they can be unsanitary if not properly maintained, and if not located far enough away from homes, can lead to contamination of groundwater. Composting toilets are the most environmentally friendly type of toilet. They use no water and turn human waste into compost that can be used as fertilizer. However, they can be expensive to construct and maintain and require a lot of space.