I never really understood how TC works. Does the TPM actually do anything on-the-fly that is noticeable? Is it used at all on any consumer devices? Fill me in

I never really understood how TC works. Does the TPM actually do anything on-the-fly that is noticeable? Is it used at all on any consumer devices? Fill me in here, because I'm at a loss. EDIT: Never mind. It seems like prior TPMs shipped with hardware, but were opt-in instead of opt-out, and now, with the W8.1 hardware spec, TPM 2.0 (which has a greater range of TC technologies) will need to be enabled as default on hardware shipped with W8.1, and there is no possible way to opt-out. A shame that hardware manufacturers are just Microsoft lackeys.