What is the Just$-$In$-$Time $($JIT$)$ system in Lean?

$$JIT is a system that suggests to produce exact quantity of each product in an organization.

$$JIT is a system that produces only what is needed, when it is needed, and in the amount needed, helping to reduce waste from overproduction and excess inventory.

$$JIT is a system that suggests that each department in an organization makes their own production schedule.

$$JIT is not a valid concept any more.