Audience

A group of people who engage with your organization and share a measurable characteristic.

The key word is measurable; "everyone" is not an audience, but "first-time visitors" or "parents" are. An audience is a real-world group that reflects the assumed needs of the individuals within that group, while a persona is a fictional representation of a single member of that audience. The audience is who they are, and the persona is how you keep them in mind.