Dart is a modern, open-source programming language that was first introduced by Google in 2011. It was created to address the limitations of JavaScript and to provide a scalable, efficient language for developing complex web applications. In this guide, we will provide an introduction to Dart, how to write it with an example, and its best applications.

The Language: 

Dart is an object-oriented, class-based language that is strongly typed, meaning that variables must have a defined type. It uses familiar syntax, similar to that of JavaScript, C++, and Java, making it easy for developers to learn. Dart supports both just-in-time (JIT) and ahead-of-time (AOT) compilation, which enables developers to develop and test their code quickly and efficiently.

Writing Dart:

Dart can be written using a text editor or integrated development environment (IDE), such as Visual Studio Code or Android Studio. To get started with writing Dart, you will need to download the Dart SDK from the official Dart website. Once you have installed the SDK, you can start writing Dart code in a file with the .dart extension.

Let's take a look at a simple example of Dart code:

```
void main() {
  print('Hello, World!');
}
```

This code defines a main function that prints the text "Hello, World!" to the console. In Dart, all code is organized into functions, and the main function is the entry point of the program.

Best Applications:

Dart is primarily used for web development, and it is often used with the Flutter framework to create native mobile applications for Android and iOS. Flutter is a popular choice for developing mobile apps because it enables developers to build high-quality, native apps with a single codebase. In addition to web and mobile development, Dart is also used for server-side programming, command-line applications, and internet of things (IoT) devices.

Conclusion:

Dart is a versatile and powerful programming language that is well-suited for modern web and mobile development. Its familiar syntax and strong typing make it easy for developers to learn, and its just-in-time and ahead-of-time compilation make it efficient for development and testing. With its growing popularity and increasing support from the developer community, Dart is a language that is definitely worth learning.