How is the explain command used in MongoDB?

The use of the explain command in MongoDB is instrumental in understanding how the database processes queries. The command provides a detailed report on query execution plans, revealing how MongoDB intends to execute a particular query, which indexes it will use, and the various stages it may go through to return the results.

When utilizing db.collection.explain().find({...}), you initiate the method on a specific collection. This allows you to see the execution details for the specified find operation, including statistics such as the number of documents examined, the time taken to execute the query, and the efficiency of index utilization. This information is invaluable for optimizing query performance and can help developers understand the inner workings of their database queries.

The other options do not represent valid MongoDB commands for obtaining query execution plans, making them unsuitable for this purpose. The correct structure provided captures the necessary syntax and functionality of the explain command effectively.