Socialism - an economic system wherein decisions about what ought to be done, where, for whom, and to what extent, is determined by a authoritarian process, usually predicated on minimisation of inequalities, and ideally managed by democracy or representative democracy.
Capitalism - an economic system wherein decisions about what ought to be done, where, for whom, and to what extent, is determined by the holders of large numbers of transferable tokens, usually predicated on the maximisation of inequalities in the distribution of those tokens (and therefore the power that they grant), and managed by the wealthiest individuals (ie those holding the most tokens) in society at any given time.
A well ordered and effective community will use a combination of these systems, as socialism is far superior to capitalism in decisions about infrastructure (in its broadest sense) and the distribution of resources that tend towards natural monopolies; While capitalism is far superior in decisions about consumable and luxury goods.
Socialism in the provision of such things as electricity, education, healthcare, water, and transportation infrastructure (roads, railways, ports, airports, etc.), coupled with capitalism in the provision of pretty much everything else, seems to be the best option.
Wherever capitalism is applied to infrastructure or natural monopolies, people suffer; Likewise whenever socialism is applied to consumables and luxuries.
Having capitalist healthcare, roads or utilities sucks.
Having socialist food, clothing, and entertainment also sucks.
There are always people who want to push their preferred system into areas where it's not appropriate. Usually they're folks who have benefited greatly from one of the two systems, and leapt to the conclusion that it's therefore got to be the best possible strategy in absolutely all circumstances.
In the modern world, socialists making this error are generally shouted down by capitalists making this error, because society in the OECD currently gives a lot of power to capitalists - particularly those in the branch of the entertainment industry that is pretending to provide information infrastructure, and that has largely overwhelmed the socialist information infrastructure that used to be in place.
There's a reason why the BBC and PBS are more respectable and trustworthy than MSNBC or CNN, and it's simply that actual news is more respectable and trustworthy than entertainment pretending to be news can ever be. It's not as much fun, though.