What does from each according to his ability to each according to his need mean?

It means that people should provide as much as they can and take what they need. It is a Marxist doctrine that in reality means that, for example, a teacher can teach others and should do it as best as he/she can. If things like bread are given out, the teacher gets according to how much he needs, based on his family size. If another person can for example provide more, like is a company chairman, but has less family members or is alone, the person will get less things given to them by the government because they don't need it.