Socialism is an economic system in which major industries are owned by workers rather than by private businesses. It is different from capitalism, where private actors, like business owners and shareholders, can own the means of production. The state can also act as a capitalist by owning the means of production and by directing the economy. Socialists believe that capitalists owning the means of production is a form of exploitation because it lets them own a majority of the labor that workers produce, even though the owners haven't done any work. By allowing capitalists to own a worker's labor, they can extract surplus value and generate profit. Socialists propose that workers themselves get to own and manage their labor.
Socialists believe that sharing ownership of the means of production equally among society would increase people's quality of life. Socialists want to give people free access to basic life necessities like food, housing, and healthcare. Some socialists also believe employment should be guaranteed as a human right. Socialists want to prevent problems that they believe come from unchecked capitalism, like poor treatment of workers and inequality. There are varying views among socialists as to how exactly the issues should be prevented. There are varying views among socialists as to how different issues should be approached. Most socialists would argue that capitalism, in its purest form, can inflict great harm.
There are lots of kinds of socialism. One big thing that splits socialists is how to make socialism happen. Reformists think people can get socialism by voting in elections and changing the government bit by bit. Revolutionaries believe that private owners are too powerful and will use their power to stop any reforms, so the only way to get socialism is to take their ownership by force.
Many groups have criticized socialism for a lot of different reasons. For example, some people think it goes against basic human nature, which they see as naturally greedy and competitive. Some are concerned about the amount of authoritarianism needed to implement socialist policies. They point to things like the lack of free speech in past or present socialist nations. And some think socialism will stifle innovation because people won't be able to profit from ownership of their inventions.