I always get confused and never got a clear picture of all these terms: parachain, relaychain, collators, validator, stand-alone node etc.

I can't figure out a way to understand connecting all these terms together. While I read over docs I have been hit by prashes like: main responsibility of relaychain is to coordinate the system as a whole, including parachains. And security is shared

I have dig into documentation several time but am not still sure what parachain is, how it related to relaychain, collators and other terms.

Can you explain how all these pieces come together. And also give an example of what happen when I do simple transfer transaction. How the block with that transfer is produced, who produce it, where it is validated, what effect it brings to parachain/relaychain and all.

2 Answers 2


You might want to check out https://polkadot.network/blog/the-path-of-a-parachain-block/

I wrote it before most of the code was implemented, so some things are out of date (e.g., there are no fishermen) and some are just implemented differently (e.g., the struct that defines a PoV). But it should give a generally accurate conceptual understanding of how these pieces relate to each other.

  • 1
    Great. I will take my time to go through the article and come back here :) Commented Jul 6, 2022 at 14:21

@joepetrowski Could you teach me why there was fishermen role initially considered to be needed and the reason it is no more exists at high level?

According to the article,

The availability check by the block author ensures that Polkadot will only include blocks for which the validators distributed their chunks, but it does not guarantee their validity. Because the number of validators on each parachain is so low, collusion is a reasonable concern. By separating block production (BABE) from finality (GRANDPA), Polkadot can perform extra validity checks after a block is produced but before it is finalized.[3] Polkadot has special actors, fishermen, who patrol Relay Chain blocks for invalid candidate receipts.

Fishermen were taking great responsibility for validity checks by pointing out potential fraud. What is the alternative for this?


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