According to Wikipedia, a Smart TV is defined as the following:Smart TVs often provide internet access, and allows us to install and run applications such as Facebook, Twitter, Skype, Youtube, Games, etc. They also provide catch up service (e.g. BBC iPlayer), personalisation and video-on-demand (e.g. LoveFilm).

The Smart TV platforms vary depends on the manufacturers.So the quality of the apps can be different. Most of the Smart TVs have preloaded apps which normally include YouTube, LoveFilm, BBC's iPlayer, Picasa, Flickr, Facebook, Twitter. If you want more, you can download from the app store. In 2010, Samsung is the first manufacturer to provide online access to a smart tv app store, followed by LG and Panasonic.