In Civilization 6, barbarians are a pretty simple obstacle to understand: kill or be killed.
In the game's next update, the barbarians are getting a complete overhaul that makes them more than just empty-headed gold pinatas. In the video below, developer Firaxis goes into detail on how it all works.
The February update, set for 25th February and free for all players, adds the new Barbarian Clans game mode. This completely changes how barbarians work in the game, adding six barbarian clans that can be found living on or near different map conditions, and each specialising in a different type of unit. You'll find the camps of the Hills Clan near hills, for example, and the Rover Clan near horses resources.
Clans can claim and build unique units from major civilisations not present in that game. These clans accumulate progress each turn to convert to a city-state. You can hinder their progress, or actually help the barbarians, learning to live together and eventually become their Suzerain.
If you destroy a clan you'll wipe it off the map, as usual. But if you raid a clan, you'll earn some gold and knock down some of their progress towards becoming a city-state. You can stop a clan from attacking your cities by paying a bribe, and even hire a clan to add its strongest unit to your army.
If a clan abducts one of your units, you can get it back by paying a ransom. You can also spend gold to incite a clan into attacking another civilisation. Exchanging gold boosts the clan's progress towards converting into a city-state.
Meanwhile, the February update adds the leader selection pool, which lets you customise the pool of leaders that can be used in-game. There are AI tweaks and balance changes, too (the bulk of AI adjustments focus on air units and air combat where they deploy anti-air defenses and engage in air strikes more frequently). Expect the patch notes alongside the update on 25th February.