Why does a support level tend to act as a 'floor'?
Support is where a decline tends to pause because buying demand clusters. Resistance is where supply clusters.
The concept: Support and resistance
Support is a level where a fall tends to pause because of concentrated demand (a floor); resistance is where a rise tends to pause because of concentrated supply (a ceiling). They matter as psychological anchors, where orders cluster, for setting stop-losses and targets, and for confirming trends on breakouts or bounces.