Technical analysis is based on the premise that you can predict the future price by looking at the past data. You can hear from the traders saying that the market is in an uptrend or a downtrend. However, observing trends is subjective. You can analyze trends from various timeframes.
Intraday traders use smaller timeframe like the 1-hour for observing trends. For swing traders, they use the daily, and the weekly chart. The scalpers use the 1-min chart.
Traders use the Moving Average indicator for finding the current trend. You can also use the RSI indicator to know about the strength of the current trend. Above 80, is considered overbought. Below 20, is considered oversold.
You can also use chart patterns like the head and shoulders, double top, double bottom, etc. to find high probable trading opportunities. Besides using trendlines, you can also use channels when the market is trending. You can trade in the direction of the trend for a better risk to reward ratio.