Models can be seen as containers for IFC file revisions much like how documents are containers for files. The difference between a model and a document is that the contents of an ifc file in a model will be fully processed with all IDs, data connected to objects and will have a generated 2D plan per storey.

Users often have one or more models per field of study.

Models can be accessed and configured on the models page in the content panel.
They can also be seen in the revision selector in the 3D viewer panel for a quick way to turn them on and off without opening the content panel.

Administrators can create models but sometimes you want to allow the modeler themselves to create new models without necessarily seeing all documents.
In this case you can allow someone to create models in project settings.

If you have gotten access to creating models in project settings you can create and delete them by clicking the new model button on the top right and the three dots next export and then delete model.