A Multipurpose Internet Mail Extensions (MIME) type is a standard that indicates the nature and format of a document, file, or assortment of bytes. A MIME type consists of a type and a subtype — two strings separated by /. No whitespace is allowed. The type represents the category and can be a discrete or a multipart type. The subtype is specific to each type. In short, a MIME-type is a label used to identify a type of data. It is used so the software can know how to handle the data. It serves the same purpose on the Internet that file extensions do on Microsoft Windows for example.
So, for Artifactory, these are used to know what files can be indexed and how. For example, by telling Artifactory that extensions "tgz, tar.gz, gz" are of type "application/x-gzip", we allow it to be able to do archive search within these files.
Some files don't have a specific type/subtype defined, so there are types for generic files.
For text documents without a specific subtype, text/plain should be used. Similarly, for binary documents without a specific or known subtype, application/octet-stream should be used.
In your specific case, the file was an unknown file format, so it was recognized as a generic binary document.
If you are making specific HTTP requests that need these files to be recognized as a specific MIME type, you may modify $Artifactory_Home/etc/mimetypes.xml to reflect this.