Demand-driven means that things are done when they are requested, which is the opposite to planned (ahead) / forecasted.
The goal is to optimize inventory and production, via the chain of requests from the ultimate consumer up to the supplier and then to their suppliers and so forth, so that each supplier only gets the material to produce what is demanded, not more, not less.
<<<<< DEMAND TO THE LEFT <<<<<<
Supplier <--\
\
Supplier <-- Supplier <-- Consumer
>>>>> SUPPLY TO THE RIGHT >>>>>
