ports vs source

[Cristi Tauber]

     Hello there,
  Can anyone tell me which are the avantages of installing from ports
rather than installing from tar balls ? I am kind of new to BSD, and I'm
familiar with linux install from tar & stuff. I know to give the
switches to configure to tune the source for installation ... but how i
can find the parameters for port install ? I mean ... let's say i want
to install php and i have to give the path to mysql, apache and others
graphical libraries ... how can I do that with ports ? 
   Any link or explications about this subject is appreciated.
       Thanks,
 
           Cristi