A sump pump is a pump that installed in a 'pit' (maybe inside a basement or outside in a drywell) that will pump out water that's collected in the pit. When the pit fills to a certain level, the pump turns on and it pumps out the water. It's all automatically controlled.
You should consider a few things. If you live in an area where the electrical power goes out a lot, or rarely but (possibly) for hours, buy a pump w/a battery backup. The battery only operates when the electricity goes out. Since you want to pump your water to the OUTSIDE of the house, and AWAY from the foundation (so the water doesn't run back down the foundation), the pump-height needs to be considered. Some pumps pump real high; others don't. This info is in the Specs. DO be aware that you need to take measures to prevent the drain line from either getting 'obstructed' (on the outside of the house by grass and such) as well as FREEZING! As an aside, the #1 cause of water in the basement is improper sloping around the foundation and leaking, missing, or improperly hung rain gutters, along with downspouts w/o an extension to get the water AWAY from the foundation. Soooo, what I'm saying is, take some time to inspect these things the next time you get a heavy rain. Don your raincoat, boots, and an umbrella, and inspect the house UPWARDS and downwards to see where the water is going. I water is running off the roof and onto the ground, fix the gutter or put one in. If water is running back towards the house after it comes out the downspout, extend the downspout and make sure your landscape is sloping AWAY from the foundation to prevent water from running back towards the foundation (and back into the basement)!!! Simple, common sense is all it takes.
Here are a few articles to read. I'm not a 'fan' of water-powered pumps. In short, you waste water from the tap to run the pump. (How ironic!) Oh, the battery will need to be replaced every few years. They cost about the same as a car battery. It's a WHOLE lot cheaper to replace a battery than it is to replace your personal belongings. So, don't let that particular cost be a factor in your decision (assuming you need/want one.) Home Depot sells the Basement Watchdog w/a Battery Backup for about $460. That's about the going rate. There are cheaper ones but I guess you get what you pay for. Maybe others can make specific recommendations for you.