Uncertainty is defined as:

After an order is placed, it usually takes time $($lead time$)$ to receive the goods. Inventory can be used to ensure business continuity during these delays.

Lead time, demand, supply, and other supply chain characteristics may be subject to uncertainty: inventory is then maintained as a buffer to hedge against this uncertainty.

A pure lean approach, i$.$e$.$ "one unit at a time at a place where a user needs it$,$ when $($s$)$ ne needs it$"$ typically incurs lots of costs in terms of logistics$.$

None of the above