Thanks for the help\
why is charging and discharging times only for timers ?
Because that the only place capacitors charge and discharge!.
Is it because the Timer shuts off and on? or has to do with the 1/3 and 2/3 comparators or the threshold input (555 pin 6) monitors the voltage?
The discharge pin is not an input, but it is listed here for convenience. It is connected to 0V when the timer output is low and is used to discharge the timing capacitor in astable and monostable circuits.
At power-up, the capacitor is discharged, holding the trigger low. This triggers the timer, which establishes the capacitor charge path through Ra and Rb. When the capacitor reaches the threshold level of 2/3 Vcc, the output drops low and the discharge transistor turns on.
The timing capacitor now discharges through Rb. When the capacitor voltage drops to 1/3 Vcc, the trigger comparator trips
Discharge The discharge pin shorts to ground when the output pin goes HIGH. This is normally used to discharge the timing capacitor during oscillation
Discharge Transistor:
The discharge transistor is turned off and therefore the capacitor Ct is charged. the flip-flop is resetted. This turns the discharge transistor on, which discharge the capacitor.