This option ensures that the publishing job is performed always or only, if it is really a new version of the published file.
If the option is checked, a check is to see if the published file is for the latest version of the file from which it was published. If the option is unchecked (default state), the publication will always be made.
This setting only applies to Vault publication. For publications outside the Vault, it is necessary to ensure for which version of the source entity the publication was created.