Zencoder
Zencoder is the creator of an open-source HTML5 video player, Video.js, built with Javascript, HTML, and CSS. Video.js plays video via native playback in all HTML5 browsers and devices, or through Adobe Flash when HTML5 playback is not available.
Flash Video
Adobe Flash Player is a multimedia and application player originally developed by Macromedia and acquired by Adobe Systems. It plays SWF files, which can be created by Adobe Flash Professional, Apache Flex, or a number of other Adobe Systems and 3rd party tools. It has support for a scripting language called ActionScript, which can be used to display Flash Video from an SWF file. Because the Flash Player runs as a browser plug-in, it is possible to embed Flash Video in web pages and view the video within a web browser. Flash Player supported display of Flash Video files since version 6, with the Sorenson Spark and On VP6 video codecs. Support was recently added for H.264 video content as well.