Governance is a special case of leadership or management.
Just like leadership it runs on information; but this time it features reporting and decision making structures that cover all aspects of a project or organisation, and not restricted to core delivery.
What do I mean?
Project governance is centrally to do with decision making that affects the delivery of the project and its relationship to corporate (owner or sponsor) priorities and mission.
The basic question of project governance is "is this project going to deliver the value that will advance the corporate mission, compared to other current or forthcoming opportunities.
In the answer to this question the risk of throwing good money after bad has to be confronted boldly. Be prepared to end a project that will not produce what an alternative use of $ will.