Final answer:
Milestones represent the critical points in a project plan that signify progress and ensure that the project is achievable, relevant, and time-bound, which are crucial for meeting project goals and deadlines.
Step-by-step explanation:
Milestones are the important points within the schedule of a project plan that indicate progress. They represent specific achievements or critical stages in the development process. For instance, in the context of engineering, imagine working on designing a new video game controller; key milestones might include completing the initial design, finishing testing, and starting mass production, all of which are tied to crucial deadlines to meet market demands. Missing a deadline associated with a milestone could jeopardize the entire project, potentially leading to cancellation or significant revenue loss. The identification of milestones ensures that a project remains achievable, relevant, and time-bound, thereby supporting the overarching goals and success of the project.