Arduino Uno v3 questions

Hi! I have an Arduino Uno v3, and i just get started with this. Some fast questions: 1. I have a led L on my arduino permanently on. Why? It`s okay? 2. What can i do with an arduino?(please give me some ideas for some simple projects :) 3. On this this, next USB connection, is a white button. What is that? Thank you!

  1. power LED or pin 13 LED?
  2. turn off or on or blink or fade the pin 13 LED.
  3. Reset

Look through the examples in the IDE (File, Examples) to see what you can do with your Uno.

Thank you! Um, i think its pin 13 LED but why the other ones dont have a LED?

Designer's implementation choice.

Some prototyping shields come with two on board LEDs. You can jumper them to any pin on the headers.