Trend Lines are one of the most basic tools used in stock trading.
Stock trend lines are used to show direction and speed of price. Trend lines also describe patterns during periods of price contraction.
Check out this image of a trend line (uptrend) straight from the trading room:
Other examples of trend lines, which are often used in options trading, are: uptrend, downtrend, trend channel, primary trend, secondary trend, and Minor Trend