The two Dead Island 2 character packs come with a skin for Jacob or Amy, as well as a unique weapon. Character Pack 1 has the 'Rodeo Sunset' costume for Jacob and 'Devil's Horseshoes' weapon. Character Pack 2 includes the 'Neurunner' skin for Amy and the 'Saimir & Julienne' twin-bladed weapon.
These character packs are included with the Dead Island 2 deluxe edition or the Dead Island 2 Gold Edition, both of which can be purchased on your console or PC storefront or at retail. These are the higher-end editions of the game and the bonuses are just new cosmetics. However, the editions do offer additional weapons, and future DLC when they are released. These cosmetics, however, will not be available in-game until Summer 2023.
As is usual today, it isn't too surprising to see these kinds of bonuses available in higher-priced editions, but the weapons likely won't be too overpowered, just helping you out in the early to mid-game. If you are interested in buying one, you can find the pricier editions of the game for around $75, £65 and $90 and £80 respectively.
So that is what is included in the two Dead Island 2 character packs. Each one offers a few nice cosmetics for you to enjoy or a new weapon to take to the fight as you use the various Dead Island 2 characters and take down the Dead Island 2 zombies types in the game's various maps.