I know what is chromecast and there is a chromecast app by google for displaying screen on the hdmi port, but what are chromecast compatible apps or google cast ready apps as described in
https://www.google.co.in/chrome/devices/chromecast/apps.html
what can we make from google cast sdk because if we can cast the screen from chromecast app,why sdk?
There is a good number of reasons that you'd want to have a chromecast enabled app rather than mirroring; for example you don't need to rely on your phone staying up, consuming battery throughout the time your movie is streaming from your phone to your TV (in mirroring mode) vs starting the movie and then even turning off your phone and enjoy the movie independently of your phone. Or allowing the whole family contributing to a YouTube playlist in the living room, or showing a presentation on your TV while your phone shows the speakers notes, or playing a turned-based game with the whole family while the TV shows the clues or ...
Mirroring/screen casting has its place but it should be considered complementary rather than a replacement to regular casting.