InstallShield is a software tool used for creating installation packages for applications. It simplifies the process of deploying software on various operating systems, allowing developers to bundle their applications with necessary files and settings. This ensures that users can easily install the software without technical difficulties. The tool supports a range of platforms, including Windows and macOS, and offers features like customizable user interfaces and automated updates. By using InstallShield, developers can enhance the user experience and reduce installation errors, making it a popular choice in the software development industry.