Captions: Watch movies, TV shows, and podcasts with closed captions. Just look for the CC icon to buy or rent captioned movies from the iTunes Store or find captioned podcasts in iTunes U. Download straight to your iPad to watch on the go. iOS also supports open captions and subtitles. You can even customize captions with different styles and fonts, including styles that are larger and outlined for better legibility. For those who are deaf-blind, iPad or iPhone lets VoiceOver users access closed caption and subtitle tracks through their braille displays.
Source: https://www.razmobility.com/ios-built-in-accessibility/#learn-more