A newsletter is a type of email sent regularly to a group of people, usually containing news, updates or other information of interest. Newsletters can be used for a variety of purposes, such as keeping subscribers up to date with the latest developments in a business or organisation, promoting products or services, or providing industry news and insights.

Newsletters are often used as a marketing tool as they are a cost-effective way to reach a large audience and promote products or services. They can also be used to nurture leads and build relationships with customers or potential customers.

To be effective, newsletters should be well-written, visually appealing and relevant to subscribers' interests. They should also be sent regularly to keep subscribers informed and engaged.

Overall, newsletters are a useful tool to keep subscribers informed and engaged and can be an effective part of a company's marketing strategy.