Asbestos is a natural fibrous material that was mainly used in construction. It was widely used as insulation and fireproofing in buildings as well as tiles, pipe insulation, boilers and garage roof tiles.
There are usually low levels of asbestos in most older buildings because of the way they used to be built, but these are very unlikely to cause any harm. However, as it ages or becomes damaged fibres can release into the air. These can be breathed deep into the lungs where they may stay for a long time, causing possible damage. When enough of these fibres are breathed in, particularly over a long period of time, there is a risk of lung diseases, including cancer.
It's usually safer to leave materials that have asbestos if they are in good condition and not damaged. You must not tamper with, drill, sand or damage it at any time.