How Does a Merkle Root Verify a Transaction without Exposing the Entire Block?

A Merkle Root, or hash tree root, is a cryptographic hash of all the transactions in a block. It is stored in the block header.

To verify a single transaction, a node only needs the transaction, the block header, and a small set of intermediate hashes (the Merkle branch). This proof, called a Merkle Proof, allows the node to cryptographically confirm that the transaction was indeed included in the block without downloading and processing the entire block's contents.