Drag and drop is a simple way to allow the users to upload their files by dropping to the container. Nowadays most websites allow uploading using both drag and drop and the file browse e.g. PushBullet, Facebook, SlideShare, etc.
I am using AJAX to save the file to the server which triggers when the file dropped on the target container.
In this tutorial, I show how you can implement the similar type of feature in your project and which show thumbnail when the file successfully uploaded.