In the world of DIY/Hobby electronics, at least for Filipino hobbyist, one will encounter these terms that are sometimes used interchangeably. Knowing what they mean would help one better digest online materials or actual conversations on Arduino.
Atmel – A lot of Arduino boards uses microcontroller chips originally manufactured by Atmel. It was taken over by the company called Microchip, the former competitor of Atmel.
Microchip – The company that has taken over Atmel.
AVR – A distinct product family of microcontrollers manufactured by Atmel/Microchip. It is based on an 8-bit RISC architecture under which are the microcontrollers that power Arduino Uno, Nano, Leonardo and Mega2560, among others.
AtmegaXXXX – These are the part numbers of the actual chips. The Arduino Uno uses the chip ATmega328P while the Arduino Mega uses the ATmega2560. Both are part of the “megaAVR” sub-family of chips under AVR.
Arduino – The development board we are all familiar with including its tool sets.