The Libraries feature was introduced in Windows 7 as part of the updated Explorer application. It allows you to consolidate multiple folders under a single Library so that content across various locations can be aggregated in a single folder-like view. By default, Libraries are disabled in Windows 10 but you can enable them. Windows 10 shows folders inside a library in the order in which you added those folders. You might be interested in reorganizing them and change their display order. Here is how.