If you remember from Chapter 1, Introducing Mongoose to the Technology Stack, a model is a compiled version of the schema.
A single instance of a model maps directly to a single document in the database. With this 1:1 relationship, it is the model that handles all document interaction—creating, reading, saving, and deleting.
This makes the model a very powerful tool.
Building the model, as we have seen, is pretty straightforward. When using the default Mongoose connection we can call the mongoose.model command, passing it two arguments:
The name of the model
The name of the schema to compile
So if we were to build a model from our user schema we would use this line:
mongoose.model( 'User', userSchema );
If using a named Mongoose connection, the approach is very similar. Using the adminConnection example from Chapter 2, Establishing a Database Connection:
adminConnection.model( 'User', userSchema );