The Arduino Mini is a microcontroller board based on the ATmega328. It has 14 digital input/output pins (of which 6 can be used as PWM outputs), 8 analog inputs, and a 16 MHz crystal oscillator. It can be programmed with the USB Serial adapter or other USB or RS232 to TTL serial adapter. With the same power, it is much smaller than Arduino Uno and more practical for building home projects.
Arduino Uno is smaller than raspberry pi microcomputer, less power but much cheaper, it can be use for many applications like learning programming and building small projects.
Arduino started in 2005 as a project for students at the Interaction Design Institute Ivrea in Ivrea, Italy. The name “Arduino” comes from a bar in Ivrea, where some of the founders of the project used to meet. The bar itself was named after Arduino, Margrave of Ivrea and King of Italy from 1002 to 1014.
The ATmega328 is a single chip micro-controller created by Atmel and belongs to the megaAVR series.It is 8-bit AVR RISC-based microcontroller combines 32 KB ISP flash memory with read-while-write capabilities.