Hi psychouvita,
 
Future perfect has the meaning of �past in the future�. It refers to something which is in the past from a viewpoint in the future. 
e.g.      I am sure that the parcel will have arrived by Tom�s birthday.
            Next year is our silver wedding: that means we�ll have been married for 25 years.
 
       i>>>>>>>>>>>>>>>>>>>>>>>i>>>>>>>>>>>>>>>>>>>>i
       i                                                    i               <<<<<<<<<<<<< i                                                  
___ i__________________________i______________________ i______________
 
       NOW                                      past in future                          future
 
 
The will 1st Conditional predicts a likely result in the future (if the condition is fulfilled).
 
e.g.      �The sky looks dark. If it rains, we�ll get wet.� �Ok. Let�s go by car.�
            If your boyfriend phones, I�ll tell him you�ve gone out with your mother.  
            ( = It is possible or likely that he will phone.)
 
Sorry about the diagram, there aren �t enough keyboard features that allow me to draw arrows here. Hope this helps.
 
Cheers,
ranclaude