The problem is simple: Just connect the dots of the same color, creating a flow between them. However, they cannot overlap!
Connect dots of the same color with pipes, creating a flow. You also have to fill the whole board with pipes to solve the level. No crossing or overlapping is allowed.
There are different board sizes to try, from 5x5 up to 10x10 and 25 levels per size, so plenty to keep you entertained. Good luck!