In attempting to answer "what is composting," we are going to start with a more technical explanation, and then proceed to answer it in lay terms.
Composting describes the controlled process of accelerating the natural biological breakdown of raw organic matter.
Now let's explain the above statement in lay terms...
In order for the composting process to proceed, you need one major ingredient: raw organic matter. This describes anything from kitchen waste, to yard waste, to animal/human waste. If you had a bunch of kitchen waste, and you dumped it into a pile, it would, over time, breakdown or decompose.
This decomposition results from the naturally-occurring microbes (e.g. bacteria, fungi, protozoa, actinomycetes) that are present in our environment. Many of these microbes are called "decomposers" because they consume, digest, and excrete organic substances. These microbes even consume, digest, and excrete one another. Therefore, if you just left your kitchen waste in a pile, eventually, it would decompose due to billions of microbes that are happily consuming, digesting, and excreting it into smaller and smaller parts.
So what is composting?
Composting takes advantage of these naturally-occurring microbes in order to help speed up the breakdown of organic waste. By creating an ideal environment for these microbes, including moisture, temperature, and oxygen, you encourage their populations to grow, and digest your waste more quickly.
For instance, if you just left your pile of kitchen wastes to decompose on its own, you may have to wait one to two years; however, if you put these materials through a proper composting cycle, you may only have to wait six weeks for them to decompose.
Finally, the most wonderful thing of all about the composting process is the end-product...
Actually, calling it an "end-product" is somewhat inaccurate, because this waste is never really finished breaking down; however, it does reach a more stable form, called humus. And humus just happens to be one of the most beloved substances by all plant life. So on behalf of your plants, please learn the ins and outs of composting, and start making humus as often as you can.
Please click on the following link if you would like to learn more about how to compost.