LPH (litres per hour) or sometimes GPH (gallons per hour) is something you must know when purchasing a pump. Flow rate is something that can easily confuse but with a little logical and practical trial, the best choice for your needs can come quite easily.
Get yourself a standard 10 litre bucket and go to the laundry or garden tap with a stop watch and simply turn the tap on at different rates and time how long it takes to fill. This may seem silly but visual confirmation of what 600 litres per hour versus 2000 litres per hour will give far greater scope to what a flow looks like.
Here is an example, the tap is running at approximately 450 litres per hour.
Running the same flow of water over a rock to break it up will make the volume look more.
If you require a larger volume like 8-10,000 litres per hour this may be more difficult but just empty the full 10 litre bucket out over the required time in seconds to create the same visual aid. For example draining the full bucket in 5 seconds equals 7200 litres per hour.
If a pump says it has a maximum flow of 5000 litres it is worth noting that this flow is without any lift. As soon as you lift the water any height through a hose (to a waterfall for example) the flow will lessen until you end up with no flow at the pumps maximum lift.