Sedimentary rocks can be used for a number of things. Sedimentary rocks form layers or stratifications. Each layer is layed down during a certain time period, so sedimentary rocks can be used to tell the geological record of an area. Scientist can tell when an organism lived through which layers its fossils are in. It's almost like looking back in time, pretty neat.
Sedimentary rocks can also be quite beautiful.
Take a look at this picture . This is one of those questions that seems simple, but scientists still can't totally agree. Some believe that the rotation of the Earth forces the water in a certain direction. However, it takes time for the force to actually work. We all know it only takes a few minutes for the water to go down the drain, so it doesn't make sense that the rotation causes it.