Private, anonymous, fungible transactions.
Just like cash but digital. And without rampant unpredictable inflation.
Discussion
But isn't that exactly what Bitcoin does?
No.
It's possible to get an acceptable amount of privacy with much friction and upkeep, but bitcoin is ultimately a traceable public ledger. And coinjoins don't make bitcoin as a whole fungible.
Reciever address and amounts don't appear on the Monero blockchain at all.
Sender and IP address are automatically obfuscated.