Guest Addition is a suite of software tools designed for virtual machines, typically installed in the virtual machine's guest operating system. These tools are designed to enhance the integration and performance between virtual machines and the virtualization platform, providing a better user experience.

• Improved display and graphics integration: Guest Addition can improve the graphics performance of the virtual machine, support dynamic adjustment of the screen resolution, and provide seamless mouse integration, making the virtual machine's monitor operation smoother and more precise.
• Shared folders: Folders can be shared between the virtual machine and the host system so that you can easily transfer files and data between the host and virtual machines.
• Time synchronization: The virtual machine can automatically synchronize time with the host system to ensure time consistency between the two.
• Better system integration: Guest Addition provides deeper system integration, such as supporting seamless window mode for virtual machines, allowing virtual machine applications to be seamlessly integrated with host system applications.
• Improved input device integration: Better keyboard and mouse integration is supported, solving common mouse pointer inaccuracy issues in VNC or other remote management tools.
• Support for hot-swappable devices: Guest Addition allows virtual machines to dynamically add or remove hardware devices, such as virtual hard disks or network adapters, while running.

By installing the Guest Addition, the operating experience of the virtual machine will be closer to the real hardware environment, and the overall performance and ease of use of the virtual machine will be improved.