TEE
A hardware-isolated environment where code and data are protected from the OS, hypervisor and other software on the same machine.
A TEE uses CPU features to isolate a workload so that even privileged software cannot read or modify it. Forms include Arm TrustZone (a secure world on phones), process enclaves (Intel SGX) and confidential VMs (AMD SEV-SNP, Intel TDX, Arm CCA). AWS Nitro Enclaves offer similar isolation using the Nitro hypervisor rather than CPU memory encryption.
Confidential computing uses TEEs to protect data in use: processing sensitive data in a cloud you do not fully trust, multi-party analytics, and key release only to attested code. Attestation is what makes a TEE useful; isolation you cannot verify is just a claim.
TEEs reduce, not remove, trust: you trust the CPU vendor, its firmware and microcode, and the attestation service. Side-channel attacks have repeatedly broken SGX guarantees, which is part of why the industry moved toward whole-VM isolation.