Full Nodes vs Light Nodes
A full node stores and verifies the entire blockchain; a light node stores only block headers and asks full nodes for details.
In depth
Running a full node is the gold standard for trust — you verify everything yourself — but it needs hundreds of gigabytes of storage. Light nodes (most mobile wallets) download only headers and use Merkle proofs to check the transactions they care about. They trade some independence for convenience.
Why it matters
It clarifies what your wallet app is actually trusting when it shows a balance.