freight trains and their purpose

[wooden birch]

What is the purpose of freight trains? To increase transport in industrial areas and reduce traffic, but what exactly do they do?
• do they carry rocket parts?
• How do I connect them? Between freight stations in remote industrial areas, or even on regular railways? How should I arrange them, in short?

[vague niche]

Fright trains somewhat reduces road traffic.
They dont carry rocket supplies, rocket supplies are only carried by trucks