Price action trading means making decisions from what the bars themselves show: where the highs and lows are, how big the bodies are, where price accelerated, where it stalled. Everything an indicator outputs is a transformation of this same data, so a price action trader argues they may as well look at the source.
Typical price action reads include a pin-bar rejecting a level, an inside-bar showing compression, a break-of-structure confirming a new direction, or a liquidity-sweep that takes out obvious stops and reverses.
The upside is no indicator-lag. The downside is that it is highly subjective: two traders can look at the same bars and see opposite stories, and there is no parameter to backtest. Written rules help. If you cannot describe your setup precisely enough for someone else to mark it on a chart, it is not a system yet.
Related: technical-analysis, pin-bar