They are pretty much the same, you can use them both in formal and informal situations without any difference. Indeed, "piacere" and "favore" are synonyms (with the meaning of "favour") Other ways to express it are, as said by JohnnyJo, "per cortesia" and "per gentilezza", which are very much more formal and far less used. "Cortesia" and "Gentilezza" can be used as abstract nouns, meaning "gentleness" (but this is not this case); but can also be used as synonyms of "favour", and it happens in the expressions "per cortesia" and "per gentilezza" Example: il tuo animo é pieno di gentilezza - your spirit is full of gentleness fammi una gentilezza, portami quel vaso - do me a favour, bring me that vase I hope that it's clear enough ^^

I would like only to summarize the answers of gianni and singleview you can have the "d" sound in two cases: - when you have the preposition "di" and a word beginning with a vowel una terra d'oltremare (a land beyond the sea) etc. however, you don't have to eliminate the "i" every time you have a word beginning vith a vowel immediately after, especially in the written language ho voglia di andare al cinema (i would like to go to the cinema) "d'andare" could be used in speaking but it's not used in the writing, it's considered not sounding great ^^ - when you have a vowel as a preposition and then a word beginning vith a vowel: siamo obbligati ad andare (we are forced to go) puoi restare od andare via (you can stay or leave) tu ed io (you and me) to sum up, in the end, it could be difficult to pronounce two vowels which are near; so you can remove the "i" of the preposition "di" or add a "d" to a vowel-preposition to have the sound "d"

i can say it in italian and french... italian: "Buongiorno" - "Come stai?" french: "Bonjour" - "Comment ça va?"

If you're asking a friend, it is: "come stai?" or "come va?" If you're asking in a formal and respectful way, it is: "come sta?" The reply the most given is "sto bene" = I'm fine