Django] I don't understanding about Nginx's advantages

I'm newbie in the dev world. I had developed small project by using Django And now trying to deploying the project from my local dev environment to the AWS EC2 instance. In addition I've choose Nginx server for performance up.

But I've a question. The role of Nginx is to serve efficiently a static files and a media files to the client. If I using AWS S3 storages for serving them, Is nginx has necessary? If so, Is there others features?