A mocktail is supposed to be a non-alcoholic version of an alcoholic drink, aka a virgin cocktail. But they've become such a huge thing, especially at bars that have large drink menus, that now they're just speciality non-alcoholic drinks. They can be anything from soda based to fruit juice based to really whatever the person creating the drink decides. The only requirement is that they be delicious, or at least that's my requirement! They sometimes use sodas like Sprite or ginger ale or something like sparkling water, mineral water, or soda water (club soda) to make it a fun bubbly drink!