I will copy and paste something I wrote in reply to a similar question in another thread:
Who said anything about a world where everyone makes the same wage?
There are two kinds of societies that people on this forum may support. The standard names for them are socialism and communism; Marxists believe that we need socialism first and communism later, after technology has developed sufficiently, and anarchists believe that we can move straight to communism right away. (note: this is an extremely simplified account of the issue)
Socialism is usually seen as a kind of society where work is the only source of income (in other words, there is no profit, interest or rent), and where some democratically elected body - which may or may not be the state - runs a planned economy for the good of all. It is also supposed to be a highly egalitarian society, but not perfectly egalitarian. People who do more work still receive higher pay. However, since your pay depends entirely on your work, differences in wealth would be very small compared to what we have now. Think about it: It's not often that you find a person who can work twice as hard as another. Under socialism, the highest income may be three or four or five times larger than the smallest income. But under capitalism, the highest income is hundreds of times larger than the lowest income (and this is due to profits, not work - but that's another story).
Communism is usually seen as a more communal kind of society, which goes one step further. It does not only abolish profit, interest and rent, but also money itself. So it makes no sense to talk about a person's "wage" or "pay" in communism. The principle of distribution is "from each according to his ability, to each according to his need". People are expected to work to the best of their abilities, and in return they can take whatever they need from a common pool of products.
Won't this lead to people working below their abilities? Only if they don't like their work. In capitalism, we spend part of our lives doing stuff we don't like ("work"), so that we can spend the rest of the time doing stuff we do like ("fun"). One of the goals of communism is to combine work and fun, so that people work because they like it - or at least because they have nothing better to do. Jobs that cannot be made enjoyable should be eliminated by having them done automatically by machines (this is one of the reasons why Marxists believe that it will take some time before we can reach communism).
Also, notice that the hardest jobs in capitalism are often the lowest paid. Some people ask, "who will clean toilets if you don't offer higher wages for such a hard, unpleasant job?" To this, I answer, "capitalism gives the lowest possible wages to people who clean toilets, and yet the job still gets done."