Recycling means turning the materials from trash into something new. Glass, paper, plastic, and metals such as aluminum and steel are all commonly recycled. Dead plants and some kitchen trash can be recycled through composting. It is important, however, not to confuse recycling with reusing, which is where old things, such as clothes, are donated or given a new use instead of being thrown out.
One reason that people give for recycling is that it reduces trash in dumps. However, too much trash is not a major problem in the United States, according to John Tierney of the New York Times. Another reason people recycle is to reduce the amount of raw materials and energy used in making things. Most of the time, it takes less energy to recycle trash than to throw it away, The Economist says.
Recycling can reduce your carbon footprint and it would help to minimise the size of rubbish tips around the world.
Source: Wikipedia (All text is available under the terms of the GNU Free Documentation License)
For more information (background, pictures, experiments and references):
Recycling: K-12 Experiments & Background Information