The concept of a stakeholder is important not only in Project Management but also in business and life in general.
The following definitions are derived from A Guide to the Project Management Body of Knowledge (PMBOK ® Guide), Page 563, 5th. Edition, Project Management Institute (PMI).
Stakeholder – An individual, group, or organisation who may affect, be affected by, or perceive itself to be affected by a decision, activity, or outcome of a project.
Stakeholder Analysis – A technique of systematically gathering and analysing quantitative and qualitative information to determine whose interests should be taken into account throughout the project.
Stakeholder Management Plan – The stakeholder management plan is a subsidiary plan of the project management plan that defines the processes, procedures, tools, and techniques to effectively engage stakeholders in project decisions and execution based on the analysis of their needs, interests, and potential impact.
Stakeholder Register – A project document including the identification, assessment, and classification of project stakeholders.