Proxy for "the people" owning all the means of production. Which means it doesn't really exist except in full blown communist states where a repressive govt owns everything - all property. It's always only a matter of time before these societies have to experiment in privatization.

The Bern has historically looked to Denmark as his "socialist" model, and govt does not own all the means of production in Denmark. Private enterprise exists, and most Danes would I'm sure tell you it thrives. So real socialism doesn't exist, and the disagreement becomes about what should be considered "public goods" that the state should make available to all. Very progressive income tax regimes with high marginal rates are thought of as socialist. Some of that is probably legit, in that it is theoretically used to pay for robust "public goods", like nationalizing all the means of providing health care, truly socializing that industry (Ocare fell way short of that). And some of it is using a label with a very negative connotation in this country to demonize the policy.

But in reality, the most left wing, radical dem self described socialists, right up to AOC, aren't truly socialists calling for govt to seize the means of American production. But they favor policies we associate with socialism, like wealth surtaxes and very high progressive tax structures, in part to provide more social services, and in part to penalize wealth just because it's wealth.