Most FTP servers including CompleteFTP use Unix-style forward slash separators in paths. Occasionally it is desirable to be able to use Windows-style backslash separators - for example if there are clients accessing the server that only support backslash separators. CompleteFTP does not support backslash separators by default, as shown below, but enabling this option enables support for backslash separators (forward slash separators are still supported if this option is enabled).
See the filesystem settings for more details.