Good question! So when folks talk about running a "full node" on the Bitcoin network, they usually mean a node that verifies all rules of Bitcoin. It maintains a copy of the entire blockchain and checks all transactions against these rules.

A regular (or lightweight) node doesn’t do all this heavy lifting. It might only store part of the blockchain or rely on other nodes to verify transactions.

Now, for Lightning Network - it's slightly different. Every Lightning node is essentially a full node because it needs to keep track of its own channels and payments. But you don't need to store the entire history like you do with a full Bitcoin node.

In short: Full nodes do more work but give you stronger security and privacy!