(IAAL but this is not legal advice, and I could be incorrect in certain aspects. Consult a licensed attorney for legal advice.)
With respect to the USPTO, I believe only patent applications can be filed confidentially. FCC applications can also be filed confidentially. But I believe trademark applications are published immediately upon filing, because the essence of a trademark is use in commerce. You don't need to file a trademark application with the USPTO to be protected by trademark law, but it is an important element of notice, which is relevant when determining certain aspects of infringement claims.
With respect to the USPTO, I believe only patent applications can be filed confidentially. FCC applications can also be filed confidentially. But I believe trademark applications are published immediately upon filing, because the essence of a trademark is use in commerce. You don't need to file a trademark application with the USPTO to be protected by trademark law, but it is an important element of notice, which is relevant when determining certain aspects of infringement claims.