Support
Definition
A price level where buying interest is strong enough to prevent further decline.
Detailed Explanation
Support is a price level or zone where a downtrend can be expected to pause or reverse due to a concentration of demand. When price approaches support, buyers are more likely to buy and sellers are less willing to sell at lower prices. Support levels form at previous lows, round numbers, and psychologically significant price points. The more times support is tested and holds, the stronger it becomes. When support breaks, it often becomes resistance.
Example
If AAPL drops to $170 and bounces three times over two months, $170 becomes established support. Traders buy near $170 expecting the bounce to repeat.