A project management office (PMO) is a management structure that standardizes the project-related governance processes and facilitates the sharing of resources, methodologies, tools, and techniques. The responsibilities of a PMO can range from providing project management support functions to actually being responsible for the direct management of one or more projects.
There are several types of PMO structures in organizations, each varying in the degree of control and influence they have on projects within the organization, such as:

• Supportive. Supportive PMOs provide a consultative role to projects by supplying templates, best practices, training, access to information and lessons learned from other projects. This type of PMO serves as a project repository. The degree of control provided by the PMO is low.
• Controlling. Controlling PMOs provide support and require compliance through various means
• Compliance may involve adopting project management frameworks or methodologies, using specific templates, forms and tools, or conformance to governance. The degree of control provided by the PMO is moderate.
• Directive. Directive PMOs take control of the projects by directly managing the projects. The degree of control provided by the PMO is high.

The PMO integrates data and information from corporate strategic projects and evaluates how higher level strategic objectives are being fulfilled. The PMO is the natural liaison between the organization’s portfolios, programs, projects, and the corporate measurement systems (e.g. balanced scorecard).
The projects supported or administered by the PMO may not be related, other than by being managed together.
The specific form, function, and structure of a PMO are dependent upon the needs of the organization that it supports.
A PMO may have the authority to act as an integral stakeholder and a key decision maker throughout the life of each project, to make recommendations, or to terminate projects or take other actions, as required, to remain aligned with the business objectives. In addition, the PMO may be involved in the selection, management, and deployment of shared or dedicated project resources.
A primary function of a PMO is to support project managers in a variety of ways which may include, but are not limited to:

• Managing shared resources across all projects administered by the PMO.
• Identifying and developing project management methodology, best practices, and standards.
• Coaching, mentoring, training, and oversight
• Monitoring compliance with project management standards, policies, procedures, and templates by means of project audits
• Developing and managing project policies, procedures, templates, and other shared documentation (organizational process assets); and Coordinating communication across projects.

Project managers and PMOs pursue different objectives and, as such, are driven by different requirements. All of these efforts are aligned with the strategic needs of the organization. Differences between the role of project managers and a PMO may include the following:

• The project manager focuses on the specified project objectives, while the PMO manages major program scope changes, which may be seen as potential opportunities to better achieve business objectives.
• The project manager controls the assigned project resources to best meet project objectives, while the PMO optimizes the use of shared organizational resources across all projects.
• The project manager manages the constraints (scope, schedule, cost, quality, etc.) of the individual projects, while the PMO manages the methodologies, standards, overall risks/opportunities, metrics, and interdependencies among projects at the enterprise level.