Resources are the materials and ingredients needed for building objects or for crafting items, weapons and food. Survivors can find raw materials by working on different tasks from either: natural sources (mines, debris, trees...) or working buildings like the wheat farm. More complex materials such as boards or weapon parts need to be crafted at the relevant work station, and some materials can only be obtained as mission loot, such as ectoplasm.
Raw Materials are resources that players can harvest from nodes on the base map, produce from buildings such as farms and mines, or find during scavenge missions. These resources are then used to craft Manufactured Materials items at various work stations
One step above Raw Materials you can find Manufactured Materials, resources that can only, or primarily, be crafted by various work stations that can be built in your base. Sometimes these resources can be traded or found in various locations as salvage, but mostly you will need to create these materials yourself.
Scavenge Materials, as their name suggests, are resources that cannot be gathered or crafted at all. Instead these materials can only be found in the wide game world, either by slaughtering certain demons or by conducting scavenging missions in specific locations that are rich with this material.
Research Materials are both rare and critical items required for unlocking higher tiers of research. Without them your survivors research and tech level will quickly fall behind the difficulty level of the demons they will be facing, leaving them with an even greater challenge to survive! Research Materials can be traded, at great cost, or acquired from scavenge missions usually within schools, hospitals, tech firms or data centres. These missions tend to be quite challenging for the tier of tech currently available.