Built-in Examples are sketches included in the Arduino Software (IDE), to open them click on the toolbar menu: File > Examples. These simple programs demonstrate all basic Arduino commands. They span from a Sketch Bare Minimum to Digital and Analog IO, to the use of Sensors and Displays.
The Arduino Software (IDE) can be extended through the use of libraries, just like most programming platforms, to provide extra functionality to your sketches. These tutorials walk your through the Examples of a number of libraries that come installed with the IDE, to open them click on the toolbar menu: File > Examples.
This section guides you though some of the key elements of the Arduino hardware and software, and the concepts behind them. What is a Sketch? What are Microcontrollers? What are the building blocks of the Arduino Programming language? Find these answers here.
In this section you can find useful information to expand your knowledge about the Arduino platform. Do you want to know what's under the hood? Here you can find guidelines for customizing every software that runs on an Arduino board and the explanation of some of the hardware design details.