Mulch is a layer of organic or synthetic material that will suppress weeds. 

If you subscribe to any newspapers, you can use your piles of old newspapers to block weeds from growing on your lawn. Start by placing 2 to 6 sheets of newspapers on the soil around your lawn plants. Add a 1-inch layer of grass clippings on top and cover it with soil.

Using newspapers for Mulch has been proven to be very effective, and it's also good for the environment because you are recycling :).