Warehouses can store materials such as Iron Ore, Rock etc. Livestock may also be stored -- Horses, chickens, hares, pigs, sheep -- which is very effective in avoiding die-off if the player cannot attend to the stables / barns / coops for an extended period. All other movable items and containers may be placed in a warehouse.
Warehouses have two means of accepting things: "open" which opens an inventory window showing the maximum and current capacity (and is for example where you can place large objects - livestock, building logs, and bulk things like ores), and "open/close" opens the door to bring in or get to other containers stored visibly within the warehouse. Items must be placed either via "open" or in a container within the warehouse.