Here are some key features of "Adobe Flash Player":
- ActionScript 3.0: ActionScript is the powerful object-oriented programming language of the Adobe Flash Player runtime environment. Based on ECMAScript, the international standardized programming language for scripting, ActionScript 3.0 further advances the language to offer developers a robust programming model for rich Internet applications (RIAs). Developers can achieve superb performance and ease of development to facilitate highly complex applications, large datasets, and object-oriented, reusable code bases. Executed within the new ActionScript Virtual Machine (AVM2) in Flash Player 9, ActionScript 3.0 delivers breakthrough performance for the next generation of RIAs.

- New virtual machine: Flash Player 9 includes a new, highly optimized ActionScript Virtual Machine (AVM) known as AVM2. Built from the ground up to work with the next generation of ActionScript, the new virtual machine is designed to deliver the performance and features to support the needs of rich Internet application developers. AVM2 supports full runtime error reporting, built-in debugging, and binary socket support so developers can extend the player to work with any binary protocol. Flash Player 9 also contains AVM1, which executes legacy ActionScript for maintaining backward compatibility with existing content.

- Increased performance
- Flash Player 9 builds on improvements in Flash Player 8 to execute content and applications faster than ever before with a number of performance improvements:
- Experience up to ten times faster ActionScript 3.0 execution with the new virtual machine and optimized compiler.
- Increase content and application speeds through faster application startup times and a 50% reduction in memory footprint.
- Accelerate rendering performance through more efficient, cached vector graphics.
- Improve text readability and get faster, smoother scrolling of large text blocks with optimized text rendering routines.
- Enhanced security
- Flash Player enforces security sandboxes for applications, content, data, and URLs to safeguard sensitive data and help ensure safe browsing for end users.

- InnovativeDisplay API: Flash Player 9 introduces powerful ActionScript 3.0 methods for manipulating raw graphics and creating custom effects. Create, manipulate, and remove objects from the display list on-the-fly.

- File upload/download: Flash Player enables the creation of sophisticated client-server applications using file upload and download APIs.

- Enhanced expressiveness
- Flash Player 9 includes the expressiveness enhancements added in Flash Player 8 that enable developers and designers to create breakthrough experiences.
- Design immersive experiences for Flash video, content and applications with full-screen mode.
- Deliver low-bandwidth, high-quality video with advanced compression technology.
- Create high-fidelity text using the advanced text rendering engine.
- Add real-time dynamic effects with filters for Blur, DropShadow, Glow, Bevel, Gradient Glow, Gradient Bevel, Displacement Map, Convolution, and Color Matrix.
- Create innovative media compositions with 8-bit video alpha channels.
- Expand your creative options with blend modes, radial gradient, and stroke enhancements.
- Dynamically import additional image formats: GIF, Progressive JPEG, and PNG.

- External API: Flash Player supports integration with HTML, DHTML, and Ajax applications through the External API.

- Asynchronous communication model: Flash Player is based on an asynchronous client-server communication model, enabling rapid client interactivity without web page refresh.

- Universal Consistent experiences: Flash Player delivers consistent content and application experiences across a range of web browsers and platforms.

- Express Install: Flash Player enables a smooth, in-context upgrade experience using Express Install and improved Auto-Update functionality.

- Input Method Editor (IME) support: Flash Player supports expanded integration with Input Method Editors (IMEs) for Asian-language Flash applications.

- Lightweight footprint: Flash Player boasts a lightweight footprint of 1MB, enabling the adoption rate of new versions to consistently reach over 600 million Internet users within 12 months of release.