According to Charles Darwin, worms are one of the most important creatures on earth. Worms are little more than intestines surrounded by muscles. Plant material goes in the mouth waste emerges from the tail. They breathe through their skin. 
This page is for those interested in learning about worm farming (w:vermicomposting). Worm farming involves feeding organic waste to special breeds of worm that thrive in decomposing matter. The worm castings (worm poo) are harvested as a rich garden manure and organic liquid fertiliser (worm tea) can be harvested.
Hobby and commercial worm farm containers can be purchased or worm farms of a great variety of shapes, sizes, designs and materials can be made.
Composting worms (with nicknames such as "Tigers", "Reds" and "Blues") can be usually be purchased in lots of approx. 1000 from garden centres and/or hardware stores or local worm farms.
A mature composting worm (which can be identified by the ring shaped swelling around their body; baby worms take about three months to mature) can consume up to its own weight each day. For example, if your organic waste averages 500g per day, you will need 500g to 1 kg of worms. There are roughly 1000-2000 worms in one 1kg. If you start with less, don't worry, they multiply quickly (they double in population every 2-3 months (in ideal conditions)).
There's lots of good info about worm farming on the web, e.g.,:
- Household worm farming guide
- Fascinating facts about worms (Can O' Worms)
- Composting with red worms
- Worm farming (youtube)
Key elements of good worm farming include feeding worms the right kinds of food in the right kinds of quantities and maintaining an appopriate level of moisture and acid/alkaline balance. This is fun to learn through reading guidelines and trial and error. Once you get the conditions right, composting worms thrive and multiply, providing an efficient and fun acceleration of the composting process.