Parents can give access to other members of their family to save documents or files in your folders and can upload documents if you give them permission to do so.
If you are expecting documents from parents, it can be easier for you to receive all of them in the same place. To do so, just right-click on a folder and choose "Get info". A small window is showing allowing you to change the folder's name, add a description, and at the top, making the folder accessible for parents.
When surfing on the last 3 columns you can visualize the type of file anytime (no matter what name it has), who has access to it and its size.