Although there are smaller variations between the two types of swimming pool, the main difference is that one will usually be constructed above ground level – where swimmers will need to climb up to get into the pool, and underground, where it can be simpler to lower oneself into the swimming area.
Regarding the smaller differentiations; these often relate to the cost, the functionality, the accessibility and the style.
In most cases, above ground swimming pools will either be temporary (the types that can be erected or blown up with a pump), or permanent (where a construction is built and the internal area filled with water. These styles can take on any shape or form and will often feature additional aesthetics such as rockeries, ladders, or even slides.