The picture at the top of this page shows methyl groups attached to the silicon atoms. This polymer is called polydimethylsiloxane. It is the most common silicone. Polymethylphenylsiloxane and polydiphenylsiloxane are also popular with the kids these days. When the real structure was discovered, it was too late, and the name stuck.
Silicones make good elastomers because the backbone chain is very flexible.
The bonds between a silicon atom and the two oxygen atoms attached to it are very flexible. The angle formed by these bonds can open and close like a scissors without much trouble. This makes the whole backbone chain flexible. If you want to know how to make silicones, click here . The mixture is soft and pliable, you can mold it into any shape easily with your fingers.