When by itself or accented, the Italian letter I is pronounced "ee," as in see or fee, but without the "y" sound at the end.
|the letter i|
|mi scusi||excuse me|
When I is unaccented and preceded or followed by a strong vowel, it diphthongs with that vowel and is thus pronounced more like "y":
|piacere||nice to meet you|
I can also affect the pronunciation of consonants that precede it: see Hard and soft vowels.