When you say
it simulates control column forces to let the pilot know it is out of trim. - the forces on the flight control are actual forces, they are just exerted on the flight controls by actuators instead of a conglomeration of springs, dampers, aeroforces, oil pressure, cables, online autopilot actuators etcetera. A computer computes what the feedback force should be, based on the position of the column/wheel/pedal. Any feel characteristic can be programmed in.
What's on board the B777 is the airborne version of what is on board Full Flight Simulators. The picture shows a sub-frame for a B737, to be built into the flight sim. Its from an old sales brochure and shows pretty sizeable electric actuators, present day ones are a lot smaller. This system was used for B737, but also for F-5, UH-60, MH-53, CN-235 etc etc.
Boeing has programmed force feel characteristics in the B777 that are pretty similar to the ones experienced by the pilots of their previous types. Since it is now all done by programming, they can add clever features such as auto-trim when the button is flicked, but on the whole the trim would still work as in all irreversible flying control systems: a mechanical spring provides forces, the trim button adjusts the neutral position of the mechanical spring so that when the aircraft is level, the control forces are zero.
The B777 is fly by wire like the A330 is, there are computers and actuators involved in deflecting the elevators, ailerons etc based on the control sitch positions, just like in the A330. But unlike the A330, the B777 has active force feedback on the flying controls, also involving a set of actuators. Note that electric actuators are fail-passive: if all power is removed, the stick can move freely and the position can still be used for fly-by-wire aircraft control, it would just feel very light.