You're looking for information on IPA apps, specifically GBWhatsApp!
GBWhatsApp is a modified version of the popular messaging app WhatsApp. It's an IPA app, which means it's an iOS app package that can be installed on iPhone devices without the need for the App Store.
To install GBWhatsApp IPA, you'll need to use a third-party app installer, such as Cydia Impactor, AltStore, or Unc0ver. Please note that installing IPA apps from outside the App Store can pose security risks, and you should only download IPA files from trusted sources.