The Symbol datatype is a legacy data type in MongoDB. It was primarily used to store textual data with some additional metadata but is now deprecated and advised not to be used for new projects.

The Symbol datatype is functionally equivalent to the String datatype. The BSON encoding of both Symbol and String is identical, but the Symbol datatype was used to differentiate these two and provide a more powerful and flexible way to extend the MongoDB system for application-specific needs.

It’s also worth mentioning that most MongoDB drivers, including the official driver, do not support the Symbol data type as a separate type. They simply map it to their string representations.

Although you might encounter Symbols in older databases, it’s recommended to use the String datatype for new projects or migrate existing symbols to strings, as they don’t provide any advantage over the String datatype.

Below is a simple example of how a Symbol was stored in MongoDB (note that this is not recommended for new projects):

  "_id" : ObjectId("6190e2d973f6e571b47537a0"),
  "title" : Symbol("Hello World"),
  "description" : "A simple example of the Symbol datatype"

In conclusion, the Symbol datatype is a deprecated legacy datatype in MongoDB that served to store textual data with additional metadata. For new projects, it’s highly recommended to use the String datatype instead.