It means that the domain extension that you would like to register requires additional documentation before it can be submitted to the Registry Office. You will have to upload documents like for example company incorporation certificate or in other cases trademark certificate of the name you want to register.
Once you order a domain name that requires further documentation, you will receive an email from our team explaining the documents that you must submit. This information is also available in “My Domain” section once you click the blue question mark next to the domain.
Notice also that the requirements of each domain extension are informed in the link “Requirement” of the domain search page.