Wealth is zero-sum. If I get more, then you have less. There's only so much physical property in the world that people can own and only so much money in circulation (even if we print more, inflation means it's always worth about the same in total). Moving things from place to place, as in buying and selling, doesn't increase net wealth, so the share market is just a way for rich people to get richer at the expense of poorer people.
Creating, however, has value. It adds value. Take something that was useless or raw and make it useful or beautiful. That is what it means to create value.
Mokalus of Borg
PS - In the very long term, I think value might need to be measured in terms of entropy.
PPS - But that's a totally different concept.