The answer to 'what causes sump pump' is that a sump pump is installed in a sump pit, which is a hole dug in the basement floor to collect excess water that seeps into the basement. The sump pump's job is to automatically turn on and pump this excess water out of the basement and away from the home's foundation when the water level rises high enough to activate the pump.
Sump pumps are commonly installed in homes with basements or crawl spaces that are prone to flooding or have high water tables. They help prevent water damage and flooding in the home by removing excess groundwater that could otherwise accumulate in the basement.