spokesperson
A person who speaks for a group or organization.
A spokesperson is a person chosen to speak publicly on behalf of a group, organization, or company. When a school needs to announce something important, the principal might act as the school's spokesperson. When a big company launches a new product, they often send a spokesperson to talk to reporters and explain what makes it special.
Spokespersons represent the views and positions of whoever they're speaking for, which means they need to understand the organization deeply and communicate clearly. They deliver announcements, answer questions, and explain their organization's thinking and decisions. If your class elected you to present your group's science project to the judges, you'd be acting as your team's spokesperson. You'd need to know the project well enough to answer questions and explain your team's thinking.
The job requires both knowledge and skill: a good spokesperson stays calm under pressure, answers tough questions honestly, and helps people understand complicated information. When a crisis happens, organizations often send their most trusted spokesperson to address the public because how they communicate can shape what people think and feel.
You might also hear the terms spokesman (for a man) or spokeswoman (for a woman), but spokesperson works for anyone.