This app store basically allows you to sideload any .ipa file onto your iPhone. That does come with the risks associated wirth obtaining apps from unknown sources, but it is nice to know you can do it.
The only requirement is that you need a Windows or macOS PC (USB or WiFi connection) for this to work for the installations themselves. There are also some specific steps to be followed to install the AltStore app itself.
A major focus of these apps seem to be 3rd party game emulators.
See
Welcome to AltStore#
technology #
ios #
altstore #
sideloading #
mobile