When you group email recipients based on common factors such as demographics, age, or purchase history, it’s called:

Grouping email recipients by shared characteristics like demographics, age, or purchase history is known as segmenting your list. This practice allows for more targeted and personalized email campaigns, leading to higher engagement and conversion rates because the content is more relevant to each specific group. Schema markup on every page of your website is a type of microdata that helps search engines understand the content of your pages better, but it's unrelated to grouping email recipients. A certain keyword density on the page refers to the frequency of keywords within web page content, which is an SEO factor and not relevant to email list management.