An IPSW file is a proprietary archive format used by Apple to distribute firmware updates for iOS devices, including iPhones, iPads, and iPod Touches. It contains all the necessary files to restore an iOS device to a specific version of the operating system. This includes the bootloader, baseband firmware, system software, and other essential components. IPSW files are typically used for updating, downgrading, or restoring iOS devices via iTunes or Finder (on macOS). The process involves putting the device into DFU (Device Firmware Update) mode or Recovery mode and then selecting the IPSW file to install. These files are crucial for troubleshooting software issues, installing beta versions of iOS, or reverting to older versions if needed. It's important to download IPSW files from trusted sources to avoid installing malicious software or corrupted firmware that could brick the device. The integrity of the IPSW file is usually verified by iTunes or Finder before installation. They are essentially ZIP archives with a different extension and a specific internal structure that Apple's tools understand.