Sure, I'll do my best. The old and deprecated DM spec, defined in NIP-04, leaks metadata to anyone who wants to see it. While the content of the messages are themselves encrypted, the information about who is sending and who is receiving is public for all to see. This on its own can be pretty destructive to privacy. The latest completed DM spec is defined in NIP-17. It is superior to NIP-04 because it uses better encryption (defined in NIP-44), and it does not leak information about who is sending the DM, only who is receiving. Therefore, anyone who is watching can only see that someone specific received a DM, but they cannot tell who they received it from. We are hopeful about a new spec that is in the works that will also make it impossible to tell who the intended recipient is, unless you are that intended recipient. It will also make private groups a possibility on Nostr. Keep an eye on what @JeffG posts about WhiteNoise for updates on the progress.