Running a node is not one activity but several, distinguished by how much history the machine keeps. What a node stores determines what it can prove without asking anyone.
The full node is the reference point
A full node downloads every block, checks every signature and every state transition against the rules, and independently arrives at the current state.
This is what makes the network resistant to authority. A user running one does not accept anyone's claim about balances, because the rules were applied locally.
The cost is bandwidth during the initial sync and continuous verification afterward, which is meaningful but well within reach of ordinary hardware for most chains.
Pruning discards history without discarding trust
Once a node has verified a block, it no longer strictly needs the block's raw data to know the current state. Pruning deletes old blocks after they have been checked.
The security property is preserved because verification already happened. What is lost is the ability to answer questions about the past or to serve history to peers.
This is the common configuration for home operators, since it keeps storage requirements manageable while retaining full independent validation of new blocks.
Archive nodes serve the questions others ask
An archive node keeps every historical state, not just every block, so it can answer what a given account held at any past point without recomputing from the beginning.
Block explorers, analytics firms and tax reporting tools depend on this. Their queries about historical balances are only cheap if someone has stored the intermediate states.
Storage requirements are far heavier than a full node's, which is why archive nodes are typically run by businesses rather than individuals.
Light clients trade verification for portability
A light client downloads only block headers and asks full nodes for the specific data it needs, checking the answers against commitments in those headers.
This gives meaningful assurance on a phone, because a proof against a header cannot be fabricated, though the client still depends on being fed the correct headers.
The weakness is availability rather than forgery. A light client can be denied information more easily than it can be lied to.
Why the mix matters to the network
A chain whose users mostly consult hosted endpoints has fewer independent verifiers, and rule changes become harder for ordinary participants to detect or refuse.
Storage and bandwidth requirements are therefore governance-relevant. Design choices that make full nodes expensive push participation toward professional operators.
This is the practical content of decentralization arguments about block size and state growth, which are ultimately arguments about who can afford to check the work.