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.
Yeah this is right definition and example of picture give the exact idea about the trend line useful post for newbies. Its the tool of technical analysis and technical analysis is not possible without using the trend like . Otherwise we can see only bullish or bearish curve without trend like. but trend like determine who much it will bearish or bullish in future.