They can be elastomers and lubricating oils. The caulking in your bathroom is probably made of a silicone. Silicones are also used to make the heat resistant tiles on the bottom of the space shuttle. Take a look at the picture on the right and you'll see how good silicones can be at deflecting heat. Back on earth, silicones are used to make hair conditioners that don't cause buildup.
Silicones are inorganic polymers , that is, there are no carbon atoms in the backbone chain.
The backbone is a chain of alternating silicon and oxygen atoms. Each silicone has two groups attached to it, and these can be any organic groups. 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.