When you file a lawsuit, your first step is to serve the person or business you have sued.

In many states, you can serve a business by serving their agent for service of process. An agent for service of process is a business or individual whose responsibility is to receive legal documents on behalf of a business. They will then deliver the legal documents to the business you have sued.

For example, larger companies like Airbnb or Facebook have a company (E.g.: CT Corporation or CSC Lawyers Incorporating Service) as their agent for service of process.

Keep in mind that the serving rules can be complicated and vary state.