What is the difference between fallback, mirror and cache directory

Question

I don't understand the difference of meaning between directory fallback, directory mirror,and cache.

Please, explain the difference.

Answer 1

It's a bit more simple than the question itself:

• Fallback equals to "when an original is not available, use replica"
• Mirror is just a network-served full cache, signed by an original
• Cache is a very local cache, that's it