A newsletter distributes news about a certain theme to a certain target group. A newsletter can be sent by post, but by e-mail is more common. Sending a newsletter is therefore often part of e-mail marketing.
A newsletter is often designed in a company's house style and contains the right tone of voice. A newsletter communicates for instance new products or services, recent developments or special actions to a certain target group. The people who receive the newsletter can be customers, but also warm leads, cold leads or prospects.