What does it mean for some companies to recruit talent reserves and trainees?

To put it simply, it means a preliminary preparation work for the far-reaching development of this unit or company, just like the current army. Although it is peaceful and prosperous now, it is still necessary to keep a lot of troops just in case. Soldiers, as the saying goes, it takes a thousand days to raise an army, but it lasts only a short time. This is the reason why companies recruit talent reserves and trainees.