Technical analysis is a method of evaluating securities using historical price and volume data rather than fundamental factors like intrinsic value. It relies on the assumptions that markets discount all known information, prices move in trends, and history tends to repeat itself. Technicians analyze charts looking for patterns and trends to predict future price movements. Key concepts include identifying uptrends and downtrends using higher highs/lows and lower highs/lows, analyzing different trend lengths, and identifying support and resistance levels where prices tend not to fall or rise beyond. Understanding trends and support/resistance allows technicians to trade in the direction of the prevailing trend.