It depends entirely on whether it's a real, credible legal claim or empty intimidation. Paste it for a read on which it is.
An anonymous/unverifiable sender, no specific conduct named, generic threats, and a pay-now demand often signal a bluff or scam with no follow-through.
If it's from a real attorney/company naming a specific right and conduct, ignoring it can lead to an actual lawsuit. Verify the sender and consider legal advice.
No — it's a private demand, not a court order. But a credible one from a real party can precede a lawsuit, so don't ignore those. Check which kind you have above.