In the inner ring, there are the validator nodes (Block-makers) that run the IBFT consensus algorithm and generate the new chain block.
In the second ring, the permissive nodes (Bootnode) are the addressed machines (enodes) well known throughout the network. Any other node, when you first connect to the network, can do so to a bootnode (or multiple nodes) and, through it, discover and connect to other nodes.
Finally, the regular nodes are responsible for replicating the blockchain, accepting the blocks generated by the validators and executing the transactions included in them. These nodes are the ones that inject transactions into the network, from sources outside the blockchain.