Types of risk

There are two types of risks to consider when investing in the stock market - the market risk and unique risks.
Market risk

The values of individual stocks often tend to move in the same general direction as the overall market. And it is unusual for individual stocks to move markedly against the movement of the FTSE 100. That's because they are all driven by the same factors that affect the overall health of the economy (inflation, interest rates, GNP figures, etc). There is obviously a risk that the market overall could fall. That is called the market risk.
Unique risk

Unique risk is specific to a particular stock. For example, if a car manufacturer's production is disrupted by a strike, it would be a source of unique risk because it would only affect that particular manufacturer. Other sources of unique risk include mistakes by company management, new inventions by a competing company and law suits.