Business Case is one of the primary documents that allow summarizing the need for launching a project and analysing possible alternatives. Throughout the lifecycle of the project this document is used to show the project justification and reasonability. In the Initiation Phase, Business Case is used as a way for making decisions on initiating the project, setting primary goals and defining the cost-benefit ratio.
Project Charter is a primary document that states contains initial requirements for a project to meet the expectations of stakeholders. Formally, Project Charter is an agreement between an organization which is committed to producing a product/service and a customer which requests and receives the product/service. Practically, Project Charter is a planning tool that helps set obligations, rights and privileges for all groups and individual involved within a project.
Successful initiation of a new project is always based on project sponsorship. If the project is well funded by project sponsors, it has the required financial foundation to carry out works, achieve objectives and produce deliverables.
Project sponsor is a person(s) or an organization(s) that is in charge of driving the project towards directions that will bring the project to successful realization of expected benefits. Project sponsor finances project initiatives and works, takes care of engagement processes, facilitates development of the initial scope and the project charter, and participates in processes of project communications management.