What is "Namespace" in MongoDB?

Namespace is the canonical name for a collection or index in MongoDB. The namespace is a combination of the database name and the name of the collection or index, like so: [database-name].[collection-or-index-name]. All documents belong to a namespace.

One can retrieve namespaces for collections experiencing slow queries on a specified host. Namespaces appear in the following format: {database}.{collection}.

Sources:

Glossary — MongoDB Manual. www.mongodb.com/docs/manual/reference/glossary.