What does the term projection mean in the context of MongoDB?

In MongoDB, the term projection refers to the process of specifying which fields should be included or excluded in the documents returned by a query. This allows the developer to control the amount of data that is sent over the network, thereby optimizing performance by not retrieving unnecessary information. When performing a query, you can specify which fields to return, allowing for a more efficient data retrieval as it reduces the size of the result set.

For instance, if you only need a user's email and name from a user collection, you would set up your query to return just those fields rather than the entire document. This can significantly reduce the amount of data being transferred, which not only speeds up the query response time but can also lower the amount of memory used by your application.

Filtering documents from a collection, while important, primarily concerns selecting which documents to retrieve based on criteria. Updating fields and creating new documents pertain to data modification and insertion, rather than data retrieval or optimization through projection. Hence, the emphasis in this context is specifically on the optimization aspect of data retrieval by selecting specific fields to return.