how automatically a collection named video gets created for our js file that we load?when do we use the other two databases(local and admin)??
You might have got steps on how to load the .js file
Once you load it you will see video in your sandbox
The main purpose of this admin database is to store system collections and user authentication and authorization data
Local stores data used in the replication process and other instance-specific data
Please see mongo documentation
You will learn more in upcoming chapters
Why the name of the collection is video on loading the movie dataset?
Video is the name of the database and the collection name is movieDetails. So when you load loadMovieDetails.js file, it loads movieDetails collection in the video database.
Let me know, if you have any questions.