Registered agent
The person or company, with a street address in the state, who takes legal papers and state notices for a business.
A registered agent receives lawsuits, subpoenas and official state mail on behalf of an LLC or corporation. California calls it an agent for service of process. Every state requires one, and you name it when you file your formation document.
The rules are similar from state to state. The California Secretary of State says the agent must be an individual who lives in California or a registered corporate agent. Delaware's Division of Corporations says agents must keep a street address and office in Delaware. A P.O. box doesn't count.
An owner who lives in the state can usually be their own agent. Many use a commercial agent instead, for a yearly fee. That keeps a home address off the public record, makes sure someone is there in business hours, and is the only option when forming in a state where you don't live.
If the agent resigns or moves, you have to update the state. California requires a new Statement of Information when the agent is no longer valid.