A descending trendline is a diagonal trendline drawn over price action that connects a series of lower-lows or lower-highs.
Descending trends are plotted over bearish trending markets in order to forecast where the price is likely to go if the downtrend continues. Descending trends are also used to indicate possible reversals in the general trend.
If the price should break above a descending trend then it can be viewed as a bullish signal. When an asset is trading below a descending trendline it’s viewed as resistance and when the price is trading above it, it’s regarded as support.