CO₂ extraction uses carbon dioxide pushed into a supercritical state — under high pressure and temperature it behaves as a gas and a liquid at the same time. It penetrates material like a gas but dissolves like a liquid.
The advantage for a producer: pressure and temperature can be tuned, so material can be pulled out selectively. And CO₂ evaporates off by itself once decompressed — there is nothing to purge.
The weakness is flavour. The conditions that give good yield usually damage the terpenes, so they often get added back into the product afterwards. That is why you mostly meet CO₂ extracts in cartridge liquid, where stability matters more than raw flavour.
Running it is expensive — pressure vessels and pumps are not cheap. That then shows up in the price.