Socialism is collectivist meaning that Socialists believe that government especially the central government and in America's case the Federal Government, should be used to make society better through social insurance programs meaning the welfare state. Things like education, health care, health insurance, pension, Unemployment Insurance, transportation, banking, energy etc. And that all these services should be provided by the central government, or that the central government should at least have a major role in providing these services.
And what government doesn't run, it highly taxes and regulates whatever private sector there is. To finance the welfare state and take care of people who don't have enough. And that no one should be able to make a lot more money than others. Even if they earned and created most if not all the wealth that they have. And that no one essentially should be able to make a lot of money compared with the rest of society and that people who make a lot of money should be highly taxed to take care of the people who don't have enough.
Socialism is very statist when it comes to economic policy and I don't mean that to be insulting. But descriptive, but socialism is more than just an economic policy. Its a fully developed political ideology that also have views on both social policy and foreign policy. Socialists tend to liberal to libertarian on social issues, just look at Canada and Sweden for example where both of those democracy's have a lot of social freedom. Way too much social freedom in the eyes of theocrats and other authoritarians in America and other countries. Socialists tend to be dovish and isolationist on foreign policy and law enforcement.
Liberalism however is very anti-statist and big government in general. And very anti-establishment as well. Liberals don't have much faith in centralized power public, or private. And believe government should be used to protect people's constitutional rights and protect people from being hurt by others. But not regulate how adults live their own lives. Liberal comes from the word liberty and when it comes to liberalism, that means freedom and responsibility for the individual. As long as they are not hurting anyone else with their freedom. And that government can be used to empower people who are down get themselves up with a hand up not a hand out. Socialism and liberalism are both progressive, but in different forms. Socialism is about empowering government to make society better. Liberalism is about empowering the people to make their own lives better.