The oplog is a MongoDB feature that tracks all operations performed on a database. Creating a user to tail the oplog with automation allows Meteor users to use MongoDB authentication to protect their database servers. To achieve this, one needs to create a new role with read permissions for the local database and then assign it to a user. The user can be configured with additional roles and credentials, which are then reviewed and deployed to the Meteor installation. Once configured, the app should provide live tracking of changes, allowing users to monitor the oplog in real-time.