Folders in Produck are exactly what you are used to: there is a folder tree with folders and nested folders that can be arranged however feels comfortable for you.
The folder tree is global to your team; if you rearrange items on the folder tree, those changes will be reflected for everyone on your team.
Folders, just like projects and sprints, have permissions settings. If you don’t have permission to access a folder, you won’t see it unless you have access to an item (folder, project, sprint) nested within that folder.
When selecting a folder, you will see cards for each project and sprint in that folder showing members, progress, and other relevant information.