"Unknown" means that the operating system does not have an identification for the creator of that file type so it doesn't know what to associate the file with. That doesn't necessarily mean that those files are malicious or unnecessary; not all applications correctly tag their legitimate files.
As Idris said, we'll need to know exactly where you're finding these files and their names before we can offer suggestions. I for one cannot read those huge screen shots you posted and what I can make out is apparently in a font other than standard ASCII so it wouldn't help even if I could read the text.
Regards.