Physical objects that have been moved, formed or processed by human labor, that satisfy desires and have exchange value. "Wealth" is probably the most mis-defined and sloppily-used term in the field of economics. In its strict definition, wealth is distinct from land (which is not produced by human labor), and from money (which does not satisfy desires). But, of course, to individuals, the distinction between land, money and wealth makes no difference, because they are all valued in the same terms. One must search the context for what people mean when they use the term "wealth".
In economics wealth or net worth of a person or nation is the value (purchasing power) of assets minus the value of financial liabilities (owed to foreigners in the case of nation) at a point in time. The assets could be tangible (land or capital) or financial (money, bonds, etc.).