Aftermath takes place roughly 20 years after a zombie outbreak that killed nearly 99% of the world's population.
Most of the "good loot" is gone - ie it's nearly impossible to find factory produced guns or ammo. There's not much manufactured food or medicine left as well to be found in the world.
Survivors are relying on their own skills and knowledge to scavenge for raw materials, craft weapons, grow food and make their medical supplies.
Survivors have been rebuilding civilization via fortifications far from the contaminated towns a creating refuge camps for themselves and other survivors.
The remaining government rewards communities that fight to "secure" nearby towns by killing zombies and restoring power by sending them "supply crates" filled with new shiny factory produced weapons, ammo and food and medicine.