Knowing that Access Control has been implemented at your site -- and understanding a few basics -- can help you to understand why certain things work the way they do.

For example, if you search for a component that you know exists, but cannot find it, then it might be due to the fact that you do not have permission to view ("Read") it. Or if you open a component, make some costing overrides in the Part Details panel, and then are unable to save it, this might be due to you not having permission to Update that component.

These are relatively obvious situations, but some types of access issues can be more subtle, such as when working with Assemblies or Roll-ups where you have Read and Update permission to most, but not all, child components.