Volatility of a stock is the amount a stock is likely to move away from the price at which it was traded at any given time.

Higher volatility means that the share price range is likely to be wider than the range for a low volatility stock.
Stock’s that move by larger margins can be more profitable on the upside, but also carry a greater risk of loss. In other words, volatility is a measure of risk.

A trader needs volatility, but must also be aware of its magnitude. The volatility of a stock will play a key part in stock selection for trading, and will impact on the effect of brokerage costs on trading profits.
Stop loss strategies will need to be considered carefully to avoid unnecessary and unacceptable losses, yet at the same time protect the trader from the inherent downside risk of volatile stocks.
it has been shown through stock trading history that volatility increases in markets that are trading downward. Therefore while the potential upside of buying volatile stocks is apparent, the downside may be even greater because the stock is trading in a downtrend. This is one of the major reasons that stocks with higher volatility tend to have a lower share price.