A mailing list is a collection of email addresses used to send information to multiple recipients at once. Organizations, businesses, or individuals often use mailing lists to share updates, newsletters, promotions, or announcements with subscribers who have opted in to receive such communications. Subscribers can join or leave a mailing list at any time, ensuring they receive content that interests them. Mailing lists can be managed through various platforms, such as Mailchimp or Constant Contact, which help streamline the process of sending emails and tracking engagement.