It won't take very long until you find yourself with a handful of characters to play in Genshin Impact. Each one has an elemental damage type that, when combined with different elements, triggers all sorts of explosive effects. Hit an enemy soaked in water with an ice spell, for example, and they'll freeze solid. Or if you aim your tornado through a campfire, it'll turn into a fiery vortex. The tutorial will explain all of this, but I really want to hammer home the point that you should be swapping between characters frequently in combat to trigger these effects.
Because you start off with only a single party member, it's easy to get locked into the habit of fighting as just one character. But by pressing the associated number key, you'll quickly swap to other members of your party. You can use this to set up devastating combos, like casting one character's water-ability, swapping to a fire character, and using a fire spell to trigger the vaporize effect. Each character also has their Elemental Burst ability, which is kind of like their ultimate attack. You can quickly trigger your other character's Elemental Bursts by pressing Alt + their associated number as long as that Burst is ready to go (an icon next to their name will indicate when it is).
Here's a handy chart breaking down some elemental damage effects:
