Support is an area, not a line. It forms where price bounced before, where a large moving-average sits, or where heavy volume traded in a volume-profile. The more times a level holds, the more traders watch it, which is part of why it holds.
When support breaks, it frequently flips to become resistance on a retest. When it holds, traders often place a stop-loss just below it.
Example: a stock has bounced from $95 to $97 three times over two months. That zone is support. A close at $93 breaks it and a rally back to $96 that fails is the retest.
Related: resistance, retest, breakout, stop-loss, volume-profile