21 BTCElectrum server
In plain words
An indexer on top of a node that wallets like Sparrow connect to.
See also
- Full nodeA full node is a computer running Bitcoin software that checks every block and transaction against the rules by itself. With your own node you don't have to trust anyone about your balance.
- Public key / xpubDerived from the private key; an xpub lets software see all your addresses but not spend.