netbox-community-netbox/docs/models/dcim/module.md

Modules

A module is a field-replaceable hardware component installed within a device which houses its own child components. The most common example is a chassis-based router or switch.

Similar to devices, modules are instantiated from module types, and any components associated with the module type are automatically instantiated on the new model. Each module must be installed within a module bay on a device, and each module bay may have only one module installed in it. A module may optionally be assigned a serial number and asset tag.