Marxism is a particular type of social and economic system in which the means of production are not owned by the wealthy but by the producers themselves. It is the idea that people own their labor and input labor and get out the equal amount of product, value and resources. That way, people are not paid less than they produce so that others can profit off of their labor instead of off of their own. It eliminates the notion of profit for profits sake and postulates that if everyone puts in labor and the products, value, resources that result are then redistributed back to the laborers in equal value to their imputs then everyone owns their own labor, effort and time rather than others being able to "exploit" laborers by essentially skimming the excess off the top which continues to propagate the status quo. Laborers can only work at one place at a time because time is one dimensional but owners can own multiple businesses at once and, therefore earn more than laborers for less physical effort.
Marxism is an idealistic economic philosophy in that it assumes that all people rich and poor want to work and will work to get what they need. It does not allow for corruption, organized crime, moochers, scam artists and the like. It has at its basis a very pro-human notion that assumes human nature is to be honest and earnest at all times. And, that by equalizing every person, no individual will possess the power that is said to corrupt.