Arduino 101 for US or Genuino 101 for the rest countries is a child of a partnership between Arduino and Intel teams. They created a new microcontroller board together and it’s twice more powerful than Arduino UNO.

 Creators may decide that Arduino UNO is quite old and needs renewal. So let’s see how Arduino UNO has changed or an Arduino 101 was created.

 Now UNO's successor comes with Intel Curie microcontroller attached on it replacing wireless connections shields for Bluetooth and Internet. Intel Curie microcontroller said to be much more powerful. And, in any other way, the Arduino UNO pinout and peripherals are provided in the board.
Curie is small and features Bluetooth connectivity and also six-axes accelerometer and gyroscope. That makes a board more suitable for wearable things. As we already said, 101 model is in twice more powerful in compare with UNO, which is clocked at 16Mhz.The board is still programmable with Arduino IDE, but you need special libraries to use Curie distinctive from UNO features.
 Needless to say, a new Arduino 101 will cost you more than a UNO board: it’s $30 in compare with $15.90. It is expected that a new Arduino and Intel product will be in the market in the first quarter of 2016 so till that time a UNO is your faithful friend.