Bulletproofs are short non-interactive zero-knowledge proofs that require no trusted setup. A bulletproof can be used to convince a verifier that an encrypted plaintext is well formed. For example, prove that an encrypted number is in a given range, without revealing anything else about the number.

Learning Path Matrix

Bulletproofs and Mimblewimble
Building on Bulletproofs
The Bulletproof Protocols
Mimblewimble Multiparty Bulletproof UTXO