Just In Time (JIT) is a production piloting system to produce:
Just the reference required,
Just the amount required,
Just at the moment required.
With minimal resources and space for:
Controlling the Quality,
Controlling the Cost,
Controlling the Deadline.
It is important to note that:
Only the production of finished products is planned.
The beginning production is conditioned by the end demands.
Each workstation takes from the workstation, at the beginning, strictly the pieces it needs.
The beginning workstation produces only the pieces which were taken.
This notion is covered in the training course « The bases of "Just In Time" ».