Some concepts are difficult to explain with words, diagrams often help, but even then it can be hard to get the point across. Carefully constructed computer presentation can help as concepts can be built and revealed on the screen.
Having a good understanding of the Critical Path and the impact it has on a project plan is very important when planning with MS Project. If you are unfamiliar with the concepts which underpin the Critical Path, or require a refresher, you may want to view my presentation on the subject. The presentation a MS PowerPoint document and includes speaker notes that accompany the screen presentation.
Download the Critical Path presentation