TPM (Trusted Platform Module) is a standard cryptoprocessor used to store cryptographic keys
Wikipedia
Trusted Platform Module (TPM) is an international standard for a secure cryptoprocessor, a dedicated microcontroller designed to secure hardware through integrated cryptographic keys. The term can also refer to a chip conforming to the standard ISO/IEC 11889.
One of Windows 11's operating system requirements is TPM 2.0 implementation. Microsoft has stated that this is to help increase security against firmware attacks.