State Plans - all employees are covered via State plans (basic plan + additional AGIRC and ARRCO plans).
Supplementary Plans - in addition, companies can also implement supplementary plans (DB plans and/or DC plans). Generally, only larger companies would implement such additional plans, and mainly for executive employees.
It is key to understand which (if any) supplementary plans exist, given that they may have to be maintained by the purchaser (depending on the insurance contract that has been signed) and they will have a cost for the employer company. The purchaser will want to understand these costs as they might impact the purchase price.