This article from the Home Advisor Website
If you live in a very flat area of the country, a place of low elevation, or a region with a high water table, then you're probably at risk for flooding—there's a reason these places are called floodplains. In fact, after heavy rains, you've probably already undergone or heard of people's experiences with flooded basements. It doesn't take much for water to cause some serious harm; in fact, just a couple inches of standing water can create thousands of dollars in damage. So in order to avoid a swamped sublevel, the best way to prevent the deluge is an investment in a quality sump pump.
Just One Job
A sump pump has one sole duty in this world: to take excess water away from your home. It may seem silly to pay money for a machine that only performs a simple, single task. But water can be a very dangerous threat to the home. Here's what happens: You have tile drains wrapping all the way around your house which captures surplus water from rainfall or heavy snow melts. When this tile gets overwhelmed, it directs the overflow to a central location in your basement called a sump. A sump is simply a well that looks like a small pit in your sub-floor where water collects.
But if this pit becomes full, you have two problems: the well may overflow into your basement, but more likely the problem is the tile around your house is just sitting full of water. And with this tile being located right next to your foundation, water may eventually seep into your basement through cracks and fissures. This is where the sump pump comes in. When water in your sump reaches a critical level, this machine will force the liquid out through a pipe that leads away from your foundation and into the city storm drain.