Adobe Flash Player
Steve Jobs also claimed that a large percentage of the video on the Internet is supported on iOS, since many popular video sharing websites such as YouTube have published video content in an HTML5 compatible format, enabling videos to playback in mobile web browsers even without Flash Player.
Comparison of HTML5 and Flash
"HTML5" in this article sometimes refers not only to the HTML5 specification, which does not itself define ways to do animation and interactivity within web pages, but to HTML5 and related standards like JavaScript or CSS 3. Animation via JavaScript is also possible with HTML 4.