In DIKSHA app, when a download a content, you will notice  an .ecar  file    also gets downloaded in the background.  

The resources (except the youtube videos) needs to be downloaded on to the device in order to access the content offline. These resources are bundled in a format called ECAR to play in DIKSHA App. So, each of these resources(contents) are individual files(with the extension .ecar) gets downloaded and store it in the file system. DIKSHA app will access the files from these folder to play that content offline.