TPM

A Trusted Platform Module (TPM) manages digital rights management (DRM) and security in a device.

Usage in Power Macs
TPM is used by Apple in PowerPC-based Power Mac G4 and G5 models to allow Mac OS X to load securely on official hardware. Many groups consider this technology to be horrible as it is closed for the sake of security. While we can't tell you how to use it, here is some basic information about the part: It's basically there to do security operations (encrypting, decrypting etc) very quickly and easily. These modules are only generally used by Microsoft, Intel, HP, and AMD. Apple uses this for its DRM and Mac OS X licensing as it is soldered onto the motherboard to be registered to that particular machine. The Hackintosh community seeks to circumvent these measures and run Mac OS X or macOS on unsupported hardware.