Timing (or boost) usually refers to a fixed amount of advance or retard applied constantly to the motor, i.e. it doesn't vary as the motor revs change. Usually this is the total of the physical timing on the motor and any boost applied by the speedo.
Turbo is additional timing based on the motor revs (when it kicks in), a time delay (before it kicks in), a slope (the rate at which the timing advances) and a limit (the maximum advance). This operates in addition to the boost timing.
IIRC the HobbyWing manual has a really good description in it.
__________________
|