Most ice cream is made by whipping a lot of air into a mix of cream and sugar while it freezes. Gelato uses more milk than cream, and the cooks whip in much less air. That makes the finished gelato heavier - if you held the same-sized scoop of gelato and regular ice cream, the gelato would weigh more.
Gelato is also served warmer. Regular ice cream usually comes out of the freezer at about -18°C. Gelato is served at about -12°C. That sounds like a small difference, but it means the gelato is soft and creamy on your tongue instead of hard and icy. The taste hits your tongue more strongly too, because warmer food tastes stronger.
Italian gelato makers, called gelatieri, take their flavours seriously. The fruit flavours often use real fruit picked the same week. Pistachio gelato should use real pistachio nuts, often from Sicily. Chocolate gelato should be made with real chocolate - you can sometimes see flecks of it.
Italians traditionally eat gelato in the evening, especially on warm summer nights, when families walk through the town centre together. The walk is called the passeggiata. Everyone says hello to everyone else. Many people are carrying a small paper cup of gelato as they go.