They are the same. The model in product catalog refers to the Hardware models (cmdb_hardware_product_model) table in the case of a hardware model that is present on the product catalog. The base model table is product model (cmdb_model). Hardware models table has a 'Publish to hardware catalog' related link which can be used to make the hardware model available in the product catalog.
Model IDs in CMDB refer to product model table. They can be created directly in the tables like cmdb_model or cmdb_hardware_product_model by clicking New or by doing bulk data load. They also get created when discovery or integrations populate records in the CMDB whose Model ID does not match the names already present in Product models (cmdb_model) table.
