What are the crates and barrels for in Goblin Camp? How to use them optimally?
Crates hold wood planks, I believe 10 wood planks per crate.
A barrel holds 10 'liquids', according to the wiki. The game will automatically put liquids into the barrels as well as put wood planks into the crates.
Ideally this is to save space in your stockpiles allowing your workers to move fewer tiles to get the items they need.