A traditional 'wet' cappuccino blends espresso, steamed milk, and foam, typically in equal parts. By comparison, a 'dry' cappuccino reduces the amount of steamed milk while increasing the amount of milk foam.
The reduced steamed milk in a dry cappuccino strengthens the espresso's bitterness, while the extra milk foam insulates the drink, keeping it hotter for longer. It also adds a lighter, frothier texture.