Voiceover is a screen reader that you can use with apple products.
This feature has been added to the operating system of Apple devices to improve accessibility for users with visual impairments, so you can use VoiceOver.
Using VoiceOver on iPhone
Go to the Settings app, enter Accessibility > VoiceOver, Turn the switch next to the feature to On, or you can use Siri to turn Voiceover on. You can do this by long pressing the home key or the on/off key on your phone.
For more information on Voiceover, see this article.