A level is a price where the market has reacted before — and is likely to react again, because other traders remember it too.
Support is a floor: a price where buyers have stepped in before. Resistance is a ceiling: where sellers have. Price tends to stall, reject, or reverse at these levels — not because of magic, but because orders cluster there.
The flip. When price finally breaks through, roles swap: old resistance becomes new support, old support becomes new resistance. A clean "flip level" retest is one of the highest-quality entries in classic technical analysis — and it echoes through Smart Money Concepts as the "breaker block."
What makes a level worth trading:
Levels are the skeleton. Everything else — order blocks, supply zones, liquidity pools — is a more precise way of answering the same question: where will price react, and why?