AVR MICROCONTROLLER Timer tutorial and example

Working with  AVR  timer  in first time maybe make us confuse . So i write this avr timer example and tutorial  as an effort for to make my understanding about AVR time more strongth reside in my memory.
AVR microcontroler has three timer :
a. Timer 0
b. Timer 1
and
c. Timer 2

These AVR timer has at least four operation mode :
1. Counter mode
2. Timer mode
3. input capture mode
4. PWM mode

To operate a timer we must deal with several register that govern these timer, below is register list that i pretend:

• Register TCNT = is counter register
• Register TCCR =register for operation mode ofsi  Timer/Counter
• Register TIMSK =register  to chose timer
• Register TIFR 
• Register OC (output compare)