The firm is the name of a company. This includes sole proprietorships, general partnerships, limited liability companies (LLC), companies limited by shares and cooperatives. Since companies are often referred to as firms themselves, it is conceptually clearer to speak of the company name. The protection of the company name is basically regulated in the Code of Obligations.
The counterpart for the individuals is the civil name. It is regulated in the Civil Code. Not only artists can invoke this protection for their stage name, but also companies.