it's a courteous form of asking. the congiuntive form. from the harshest - direct to the most courteous: Dammi due birre - "tu" is the object, imperative form - give me two beers Mi dia due birre - "lei" is the object, the form is congiuntive Mi potrebbe dare due birre? - the phrase is a question, which is politer, the subject is "lei" form instead of "tu", and demand is mitigated by that "potrebbe" : could you give me two beers? that "Mi dia due birre" kind of sentence isnt really translable in english as well as the other two. It is a midway form between the direct imperative and the polite form because of that "lei" and congiuntive. moreover: una birra= just one beer, delle birre = several beers.

/dia/ is the imperative mode, the mode for giving orders; da' as a third person is indicative mode, that is the mode for describing reality, and not hypothesis or wishes; Answer (all correct forms) a) mi dia delle birre, per favore b) mi da' delle birre ? c) vorrei {una birra, delle birre} [per favore] I don't drink beer (as it has alcool), but I would use (c). Another you will hear is: d) volevo una birra ... here a fake past tense is used to mitigate the meaning of a direct order to the bartender; it's commonplace. About imperative: if you walk around with a friend, and see something interesting, you just say: /guarda la'/ (look there) or /guarda un po' la'/, in the imperative mode; it is perfectly fine as you are making an order in behalf of your friend. Imperative mode is the mostly used among friends and between Captain and Soldier.