Capital

Money available to purchase assets that can be used to generate more wealth.
or
Assets that can be used to generate more wealth.
Capital in this sense may include property, machinery, or other assets that produce things that can be sold for income.
Income from capital is taxed differently to wages. This is one reason why the richest kiwis can pay less tax for each dollar they get.
Visual idea: A seed growing into a tree labelled “investment → income.”