IT Governance at its heart is about accountability. It is a set of rules and standards that establishes how decisions are made, who can make them and at what level their authority ends. It also establishes escalation processes. It ensures that IT stays connected to the corporate strategy.
The single most important group to establish IT accountability is the IT Steering Committee made up of the senior executives of the company. While the committee is not involved in day to day operations it is responsible for setting the general direction and allocation of IT resources. It is here that the IT strategy maps to the corporate strategy.