GFS - Global Forecast System
This version of GFS is very similar to the normal LuckGrib version, except that rather than being served by the fast LuckGrib server cluster, the data is obtained directly from NOAA.
Data obtained through this technique is quite a lot slower than the normal LuckGrib server. However, when you use this access method, you will have access to the entire GFS model - over 300 parameters.
If the data you want is supported by the LuckGrib server cluster, you should use that data access method.