Folders are fairly simple creatures, but they are the backbone of file system organization.
Modern computers have millions of files organized into thousands of folders.
Without folders all those files would be in one place and it would be impossible to look through that many files to find the one we need.
With folders, we can set aside space for our own files, separate from all those other files and folders, so they don't get mixed up.
And we can create our own folder tree structure to organize all of our many files in a logical way that we can keep up with.