From a high level, a project represents a group of related tasks that create a unique result, product, or service. A project must have both a beginning and end point. Without these, the tasks involved are part of ongoing work and are therefore not part of a defined project.
Note: During the exam, it is important to remember that a project is time limited (with both a beginning and end), that it is unique (has not been done before by the organization), and that it is being undertaken for a specific purpose. Expect several questions on the PMP certification exam to ask you “Is this a project?”