Andreas Griffin on Nostr: It pulls a summary of the blocks from normal Bitcoin nodes. If an address of the ...

It pulls a summary of the blocks from normal Bitcoin nodes. If an address of the wallet is in the summary, then the wallet pulls the entire block.

This is fast, because only a few blocks need to be pulled.
And it is private, because in each block are 2000+ transations, and it is not easy to determine which one you were interested in.

https://bitcoinops.org/en/topics/compact-block-filters/
https://ellemouton.com/posts/bip158/