Keeping and improving production chains, making sure you never run out of a resource is naturally of the utmost importance, but it’s not always possible to organize everything to work without a hitch. This is your stockpile comes into play.
Warehouses and depots, beside increasing your stockpile space (inventory) also serve as points where your carriers and workers can drop off produced or collected resources and from where they can pick up what is needed elsewhere. Make sure to create an efficient and sustainable coverage of all your production and housing buildings. If your warehouses and depots are spread too thin, your Citizens will need to travel farther to get what they need, thus reducing efficiency.
The other benefit of warehouses, as noted above, is increased stockpile space, meaning you can store more resources. This makes it possible to withstand longer periods of a resource scarcity, but also to go into grand construction projects. For example, if you have enough construction materials stored (Lumber, Stone, Bricks, Iron, Tools…), you can build many structures in a short period of time. Another good example is food. Food income is not constant. Fields can’t grow crops during the winter, fishing efficiency is lower during droughts etc. You should always have enough food in storage for such situations. Plan ahead!
A notable element of the Stockpile panel is the Set cap field. This makes it possible to limit the maximum storage space for any specific resource.