Yes, in a stock iOS installation Apples App Store is the only way to install software. Each package must be digitally signed by Apple. That is what 'jailbreakin

Yes, in a stock iOS installation Apples App Store is the only way to install software. Each package must be digitally signed by Apple. That is what 'jailbreaking' is all about: exploiting a flaw in some existing software to execute an arbitrary binary which breaks that restriction. Then you can use third party software repos.