The European Commission is the only EU institution which can initiate legislation. Before it can propose new laws, it has a duty to consult with interest groups and experts to ensure the interests of the European Union as a whole are served.
Once the commission has formed a proposal, either for a new law or for the annual budget, it submits it to the European Parliament and the Council of Ministers to pass or reject it.
The parliament also has responsibility for supervising the 20 commissioners and is the only institution with the power to sack them. Commissioners are appointed by the Council of Ministers and then approved by Parliament.
Once legislation has been passed, the Court of Justice makes sure it is interpreted uniformly across all the member states and tries to iron out any differences between European and national laws.
The Court of Auditors is the watchdog for the budget, checking that the money is being well spent and trying to give European citizens value for money.