The tax is based on an LLC that is not taxed as a Corporation. For entities that elect to be taxed as a corporation they File Form 100 and their tax is determined under the CA Revenue and Taxation Code beginning with Section 23001.
Any individual seeking legal advice for their own situation should retain their own legal counsel as this response provides information that is general in nature and not specific to any person's unique situation. Circular 230 Disclaimer - Advice given in this response cannot be used to eliminate penalties with the IRS or any other governmental agency.
LLCs cannot be S-Corp's. S-Corps are an election for Corporations, not limited liability companies. Before you form a corporation or LLC you should consult a tax attorney or accountant to determine which is better based on your planned business and the revenue, expenses and profit expected and other options.
Please note that this answer is not legal advice, and should not be relied upon. Each state has different state laws and procedures. A review of all documents and a consultation at a minimum is necessary to render effective legal advice. This answer does not create an attorney client relationship. Consult an attorney before you decide on a course of action.