Trend lines are drawn on charts to help predict the general direction of price.It also help to determine good entry and exit point.they also help to see the reversals.
Trendlines are straight lines that connect each successive rising bottom to show an uptrend or each consecutive declining top to indicate a downtrend. There should be 2 price points for the trendline to be drawn. The longer the trendline and the more points it connects the stronger it can support/resist the prices on subsequent tests - because more market participants are aware of it