Frequently Asked Questions
IPSW, iPod Software, is a file format used in iTunes to install iOS firmware. All Apple devices share the same IPSW file format for iOS firmware, allowing users to flash their devices through iTunes on macOS and Windows.
Just search for it on Google, you'll find every post you need.
iTunes will stop the process if it detects that you have the wrong file for your device. The only thing it will cost you is another download, so please read carefully.
From the Apple Developer Center.
You aren't downloading the file from me. You are downloading it directly from Apple, as proved by the URL it downloads from. Also, if they weren't, iTunes would refuse to install them, as you cannot install modified IPSW files.