Thanks for the welcome.
The link is good, but doesn't make things very clear. The Attitude Heading Reference System drives your HSI or EHSI and your ADI or EADI. It can also provide information to the autopilot system. On some aircraft, like the T-6A, it provides information to the Trim Assist Device (not 100% sure the D is for device, though).
The systems I work with are solid-state, fiber-optic gyros. Some of the more sophisticated ones can operate as Inertial Reference Systems.