Dartpad is a browser-based text editor that can execute Dart code, created by the Dart team. It's a "playground" or "scratchpad" of sorts, useful for testing small pieces of code. If you're just starting out with Dart, you can use Dartpad to get your feet wet without having to install the Dart SDK and IDE plugins.

It's features include a linter, analyzer, and embedded web view, enabling you to play with HTML and CSS along side your Dart code. Dartpad is a resource that would be useful to use while following along with examples and tutorials on Flutter By Example.

On Flutter By Example, we'll make heavy use of DartPad, and it's embedded right in the page, so you never have to leave the page. It looks like this when embedded in the page:

    
        main() => print("Hello, World!");
    

If you'd rather work in your own text editor, you can find instructions to install Dart on the Dart homepage.