Inside of your skimmer, there is a plastic gate called the weir. The weir is a very small part that makes a very big difference in how clean your pool looks through out the week. Its amazing how often I see the skimmer missing its weir gate and how many people, including pool technicians who clean pools every week, that don't know what it is, or what it does.
The weir gate is simply a way to keep the debris that is sucked into the skimmer, from getting back out into the pool. While the pump is on, the weir gate will be pulled back as water comes into the skimmer and just like the name describes, the water skims over the top of the weir. Styrofoam makes the weir gate buoyant, so when the pump shuts off and there is no longer water pulling across the top of the weir, it stays upright in the skimmer trapping the leaves inside.
Weir gates can break when they become old and brittle, or from a lot of splashing when kids are swimming. If the weir gate is broken, or missing, it should be replaced. You will have a cleaner pool and reduce the time required to net each week as long as the weir is functional.