Support is a price area where buying has repeatedly overwhelmed selling, halting declines. Resistance is the opposite - where selling repeatedly caps advances. Draw them as zones, not exact lines: they are regions where the balance of orders tends to shift.
Why they form at all
Levels are not mystical. They form because real orders cluster there: prior highs and lows, round numbers, the previous day's range, the opening range, and areas where large participants have resting interest. When price returns to a level where a lot of business got done, it often reacts - because the same buyers and sellers are watching the same spot.
They break - and that is information
The mistake is treating a level as a wall. Levels break constantly. What matters is how: a clean break on rising volume says the balance genuinely shifted; a poke through that immediately reverses (a "fakeout") says it did not. A broken resistance level often becomes support afterward, and vice versa - old battlegrounds get re-fought.
A level is not a prediction. It is a place to watch how buyers and sellers behave when they get there.
Levels plus context
Support and resistance are far more useful combined with context: the VWAP, the day's volatility regime, and dealer positioning that can amplify or dampen a move (see gamma exposure). A level tells you where something might happen; structure and flow tell you whether it is likely to hold. That layered read - level plus behavior plus positioning - is what separates a plan from a guess.