The net API provides access to network information of the node
The clique API provides access to the state of the clique consensus engine. You can use this API to manage signer votes and to check the health of a private network.
The debug API gives you access to several non-standard RPC methods, which will allow you to inspect, debug and set certain debugging flags during runtime.
The les API allows you to manage LES server settings, including client parameters and payment settings for prioritized clients. It also provides functions to query checkpoint information in both server and client mode.
The txpool API gives you access to several non-standard RPC methods to inspect the contents of the transaction pool containing all the currently pending transactions as well as the ones queued for future processing.
The admin API gives you access to several non-standard RPC methods, which will allow you to have a fine grained control over your nodeinstance, including but not limited to network peer and RPC endpoint management.