Ember.js is a popular open-source JavaScript framework used to build scalable and maintainable web applications. Developed by Yehuda Katz in 2011, Ember.js has become a popular choice among developers due to its powerful features and simplicity in creating complex web applications.

Ember.js follows the Model-View-ViewModel (MVVM) architecture pattern and provides a complete set of tools for building large and complex applications. It is built on top of the Handlebars templating engine and uses the Object-Oriented Programming (OOP) principles to manage the application's data and logic.

One of the most significant advantages of Ember.js is its ability to handle large-scale web applications. It provides a robust set of conventions, allowing developers to focus on building features rather than worrying about how to structure the application. Ember.js also provides built-in support for two-way data binding, allowing changes to the data to automatically update the view and vice versa.

Ember.js also comes with Ember CLI, a powerful command-line interface that automates the development process. Developers can use Ember CLI to generate code, run tests, and deploy the application to production with ease. The Ember Inspector is another useful tool that allows developers to debug and inspect Ember.js applications in real time.

Ember.js has a vibrant and supportive community that provides extensive documentation, tutorials, and plugins. The Ember Addons ecosystem provides a vast range of add-ons that developers can use to extend the functionality of their applications. The community also actively contributes to the framework, adding new features and fixing bugs.

Ember.js also supports testing out-of-the-box, making it easy to write and run tests for the application. Ember.js has a testing library called Ember Testing, which provides powerful tools for unit, integration, and acceptance testing.

However, like any technology, Ember.js has its drawbacks. Ember.js has a steep learning curve, and developers must invest time in understanding the framework's conventions and patterns. The framework's strong opinions may not be suitable for projects that require more flexibility in terms of architecture.

In conclusion, Ember.js is a powerful and robust JavaScript framework suitable for building complex web applications. Its extensive set of features, conventions, and plugins make it an excellent choice for large-scale projects. Although it has a steep learning curve, the Ember.js community provides extensive documentation and support, making it easier for developers to get started.