iOS/iPadOS device backups include a record of the installed Apps - and includes the associated App data. The Apps themselves are not included in any of the available device backup options.
This limitation is in part due to digital signing of Apps; Apps installed on your devices are [individually] digitally signed by Apple - and are associated with both the specific device upon which the App is installed - and the AppleID that was used to purchase the App licence. This identity-pairing prevents unauthorised/unlicenced transfer of Apps between devices or users - as a fresh copy of an App must be obtained from the App store when re-installed - this copy being similarly uniquely digitally signed.
When restoring a backup to a target devices, Apps that are both (a) compatible with the target device, and (b) remain available for download and install, are automatically reinstalled from the Apple App Store.
This support page outlines the natively supported backup methods for iPad and iPhone:
How to back up your iPhone, iPad, and iPod touch - Apple Support
Native iOS/iPadOS backup and restore processes are dependent upon iCloud, or connection to either Windows PC (with iTunes for Windows installed - or more recent Apple Devices App) or a Mac computer (with iTunes or Finder - as appropriate for the installed version of macOS).
Natively supported methods offer full system backup - consisting of data and device settings.
How to back up your iPhone, iPad, and iPod touch - Apple Support
It is possible to use a third-party App to backup data (but not device settings or Apps) to a variety of external storage options - including third-party Cloud services, external media devices and network storage. By example, FileBrowser Professional by Stratospherix:
https://apps.apple.com/gb/app/filebrowser-professional/id854618029
There is an extensive online Manual:
https://www.stratospherix.com/products/filebrowserprofessional/filebrowser-professional-user-guide.php