Android apps  are basically comes as APK files.Here I am going to explain how to download APK file using Google Play. Sometimes you don't want to use your Mobile data pack to download Android apps then you can use your Broadband Internet on desktop to download it and later you can install on Android device.

This trick will help where:

Sometime Google Play Store says that a particular app or game is incompatible with your Android device though you know that the app would work just fine in that case this trick is useful

Sometime an Android app may be not be available for download in the Google Play store of your region or country.
 An app on the Google Play store but you want to install that app on another Android device, like the Amazon Kindle tablet, that doesn’t have the Play Store.

Google Chrome desktop browser and Chrome for Android include now support for WebRTC (Web Real Time Communications), an emerging web standard that helps  real-time audio and video capabilities to their web applications without the need for plug-ins or proprietary codecs.
There are various  apps has capabilities like voice calling, audio & video conferencing, video broadcasting, screencasting and screen sharing in the browser via simple JavaScript without requiring plugins.

Some of  web apps are like http://same.io,http://talky.io http://appear.in to Video /Voice chat Screen sharing without  installation or download anything. Only you require is the latest Chrome browser.

There’s a little setting in Chrome that you need to enable . Type chrome://flags in your Chrome’s address bar, find the setting that says “Enable screen capture support in getUserMedia()”, click the Enable button and restart your Chrome browser.