You can view not only the current part you are working on, but all the other parts of the assembly.
It can help you to have a better overview of the whole assembly/project and work more efficiently.
To change the part of the assembly:
1. Click on the drop-box called "Assembly PDF"
2. If there are additional parts you can scroll and find the part you want to view.
3. If there are too many parts search using numbers of the right to sort the parts, and when you see the one you need, click on it.