AltStore is a tool that helps users install external IPA files or install applications outside the App Store on iPhone and iPad.
After being installed with AltStore, the application's certificate will be revoked after 7 days, but you just need to connect to the computer that has installed AltStore and select Refresh to re-issue the certificate and continue using it without having to delete the application and reinstall it, like installing files via Sideloadly or Cydia Impactor.
To use AltStore, your device does not need to be jailbroken, and you will not have to worry about the security risks of the device after jailbreaking. You only have to worry about installing fake IPA files of unknown origin with this tool.
