Administrators and uploaders are able to upload files on Meta, while regular users are not. This was done to reduce the increasing amount of junk and copyright violations present in Meta files (and reduce the existing ones), while allowing certain members of chapters and users with legitimate interests to continue uploading there things which would not belong to Commons' scope (T52287).
Upload files (upload)
Overwrite existing files (reupload)
Overwrite existing files uploaded by oneself (reupload-own)