Need explaination: Phone Vs modem

[sirc saira]

Dear Guys, 
  I need some explainations.

  Which is better a phone or a modem? 
  A phone does have a modem, right? Can a sim card (with number xxxx-xxxxxxx) 
inserted in a modem? 

  So how does kannel work with a modem?

   thanks guys
cris arias