Dual-booting is a setup that allows a computer to run two different operating systems, such as Windows and Linux, on the same machine. When the computer starts, users can choose which operating system to load, giving them the flexibility to use software and features specific to each system. This method is useful for those who need to use applications that are only available on one operating system or for developers testing software across different environments. Proper partitioning of the hard drive is essential to ensure that both operating systems can coexist without interfering with each other.