Once upon a time, online video delivery was unquestionable dominated by Flash Video. And it was mostly good. But Flash had various flaws: it required a plugin to be installed on the browser, it consumed a lot of power from devices and it was not liked very much by Apple. So the flash plug in was banned from Apple mobile and tablet devices, and soon other devices followed suit and simply stopped supporting Flash. Flash video players were left out of the mobile arena. Parallel to all that, and taking it into consideration, the World Wide Web Consortium (W3C) were developing the HTML5 specification which included HTML5 video. It is a video element for the purpose of playing videos or movies without any plug-ins. Browsers that support HTML5 must support HTML5 video.
Aside from the format troubles that maligned the various HTML5 Video is here to stay.
Traditionally in order to make a 2 way video call the options are limited to two ways: a video client/app such as Skype or a browser plug-in based application usually created with Flash. The problem of course is that any such options must be supported by both callers (both must have Flash or Skype installed). Enter WebRTC.
WebRTC (Web Real-Time Communication) is an API definition drafted by the World Wide Web Consortium (W3C) that supports browser-to-browser applications for voice calling, video chat, and P2P file sharing without plugins.
In other words, video calls will be possible without the need of any program other than the web browser.