A Trusted Execution Environment (TEE) is a locked room inside a processor where code runs encrypted in memory—even the server owner with root access can’t see what’s happening inside. The TEE produces an attestation: cryptographic proof that specific code ran on real hardware without tampering. This matters for private inference: you send your prompt to an AI model inside a TEE, and the server operator literally cannot see your input or the model’s output. It’s also used for VRFs (Verifiable Random Functions) in crypto—proving a random number was generated fairly, not manipulated by the house. Intel SGX and AMD SEV are common implementations. The trade-off: TEEs add overhead and have had side-channel vulnerabilities, but they’re the best “don’t trust, verify” option when you need to run sensitive code on someone else’s machine.