Cement.....So what is it exactly?

Cement seems to be on everyones lips lateley, due to the excitement generated by the Astonomical success of ENU. But what exactly is it?

The cambridge press Dictionary defines it as follows ;

cement (BUILDING MATERIAL) [Show phonetics]
noun [U]
a grey powder which is mixed with water and sand to make mortar or with water, sand and small stones to make concrete:
a bag of cement
a cement factory

Cement can be used to make a fountain in your garden, to get rid of unwanted tenants in your rented accomadation, and as a foodstuff to feed to the poor.

Apparently you can also use it for these........