Questions
Yes-or-no questions need only rising intonation; information questions start with a question word.
A yes-or-no question uses exactly the same word order as the statement — only your intonation rises at the end: Parli inglese. (statement) becomes Parli inglese? (question). No auxiliary like do is needed.
Information questions put the question word first: chi (who), che cosa or cosa (what), dove (where), quando (when), perché (why), come (how), quanto/quanta/quanti/quante (how much/how many), quale/quali (which). Dove abiti? — Where do you live?
Perché means both why and because; the context or question mark tells you which. Quanto agrees with the noun it asks about: quanti anni (how many years), quanta gente (how many people). Before a vowel dove and come can elide: dov'è, com'è.
Examples
- Parli italiano? Do you speak Italian?
- Dove abiti? Where do you live?
- Quando parte il treno? When does the train leave?
- Quanto costa? How much does it cost?
- Perché studi italiano? Why are you studying Italian?
Common mistake
Importing English do (Fai parlare italiano?) — Italian asks with intonation alone: Parli italiano? Adding fare creates a different meaning (making someone speak).