[E] The Bollinger Bands Indicator VI

If price reaches the upper band, this means it is relatively high and the asset could be overbought. You could look to sell an overbought asset on the assumption that its price will fall towards moving average.
Conversely, if price reaches the lower band, this means it is relatively low and the asset could be oversold. You could look to buy an oversold asset on the assumption that its price will rise towards the central moving average.