What are the x-chain?

Marketplace Primecoin
1

I observed 6-chain, 7-chain, 8-chain, etc.

What this is?

Is it related to “-poolshare=6”?

Thanks

2

Those are the number of chains that you find of different lengths. The number corresponds to the length of the chain, which is the number of primes in the chain. The chains that are shorter than the current difficulty will not be used to mine a block, but they can be used to give you an idea of how fast you are finding chains and it is also used by pools to prove that you are doing work.

I assume -poolshare=6 tells the client to try to find and submit chains of at least length 6.