1- AVR : What is MicroController

Microcontroller is a controlling device . it's like a computer without monitor , voice card , ... . but it has software and can control the circuit . for example if I want to make a blinking led or show the temprature .
AVR is a product of Atmel . we have three sorts of avrs.

1. AtTiny
2. At90s
3. AtMega

AtTiny is the smallest of AVR family
AtMega is the most powerfull device in AVR family .
we already use atmega16 a member of AtMega family

please make me suggestions in the comments