An uptrend is made of higher highs and higher lows. When you draw a line connecting two successive lows, then you get a support line or a bullish trendline. Each time the price visits this line, it acts like support, and pushes the price higher. Again, when you draw a line connecting the highs, then it is called as the resistance line. It pushes the price lower to look for support.
At some point, due to the shift in fundamentals governing the asset, the market changes direction, and breaks through the support line to proceed downwards. You can trade the breakout of this bullish trendline.
In a downtrend, you can connect the highs to draw a bearish trendline or a resistance line. By drawing a line parallel to this trendline, you get a channel.
When price moves sideways, then you get a horizontal support and a horizontal resistance line. When price reaches the support line, the price gets pushed to the upside, and meets the resistance line. Similarly, the resistance line offers resistance, and pushes the price downwards. Make sure that you use a