A Regression line attempts to describe and fit data distribution in a single line, and thus summarize and present the distribution of the data in a single line.
Accordingly, for traders, price should readjust towards this line when a deviation is seen.
AMAZON shares are trading 4-std away from its regression line, although i have a bearish bias, there is nor confirmation of a reversal yet. It is a good idea to zoom into the daily chart and wait for a support break before shorting