A fund (n.) is a source of supply or a reserve (usually pecuniary or money) to facilitate something. Often in reference to a large-scale or long-term project. In financial markets, funds (such as mutual funds) are organizations or closed entities that manage investments with a specific goal, market or method.
As a noun, fund refers to one of several accounts used in governmental accounting.
To fund (v.) is to provide the financial wherewithal (i.e. the funds) to support a project through to its completion.