On this picture you can see Raspberry Pi computer with arduino control board. (control board is a hand made 2 layer board, sorry for this terrible work.)

Arduino board can be used as standalone control board, without Raspberry Pi computer and can perform low level tasks such as path planning, obstacle avoidance, line following, remote control. In addition with Raspberry Pi computer, robot gets much more complex functionality such as: object/face recognition, speech synthesis, Speech Recognition, dynamic programming and etc.
robotics kit can be controlled and programmed wirelessly, In final design, robotics kit can be programmed with wide variety programming languages (python, javascript, c, c++, perl, c#) and visual languages like Google Blockly and Scratch.