Price action, or just "action" is a way of analyzing charts visually without indicators. It's like a language in itself. I'll give a few examples.
"longs putting pressure on short spec..."
"forced short covering getting sold off"
"forcing longs out of the market"
"accumulation"
"sizing in/scaling out"
"ranging at the new level"
"setting up a range"
It's really just advanced trader talk that doesn't use indicators to make decisions.
It's also called, "reading the market" or "getting a read" and it can be used to do a lot of stuff like predict breakdowns, relief rallies, ranges, and even volatility.
Basically, advanced traders don't need indicators to read the market. They may still use them but they don't always use them.