In total, an A320 has 7 flight control computers that process pilot inputs according to 4 different modes of operation, called LAWS:
1) Normal Law
2) Alternate Law
3) Direct Law
4) Mechanical Back Up
In Normal and Alternate Law, pilot commands are processed from the computers and then converted to flight surface movement. In reality an Airbus pilot when moving the sidestick asks for “G’ load” in Pitch and “roll rate” in Roll. The computers will calculate the appropriate control surface deflection and actuate them. Furthermore, the aircraft doesn’t need the pilot to trim it to maintain a given attitude. The FBW will auto-trim the control surfaces to maintain both pitch and bank. (It is strange though that the B787 has trim controls on the control wheel…)
In Direct Law, the control surfaces movement is directly proportional to the sidestick movement.
All control surfaces are electrically controlled and hydraulically activated.
All primary control surfaces have at least two hydraulic actuators (for redundancy) which receive electrical signals (orders) from the flight control computers.
Only the Rudder and the Trimable Horizontal Stabilizer have a direct mechanical link to be used as a last resort, provided hydraulic power is available.