L2J Server

I'm new begin for L2server.
can you explain me how different of import net.sf.l2j.gameserver and import com.l2jserver.gameserver?

Ex.
import net.sf.l2j.gameserver.xxxxxxx;
import com.l2jserver.gameserver.model.xxxxxxx;

Thank you

net.sf.l2j.gameserver is the packet declaration for Gracia Final and previous L2J revisions.
And com.l2jserver.gameserver is the current declaration for Freya also it was for Epilogue.

If you are moving code from Gracia Final to Epilogue or Freya you can try replace those declarations, if you are using Eclipse you can try deleting the whole line and go to the suggestions tool tips how to fix that unknown type/class/method and click on Import ClassName.java from...