Callouts are a type of visual element commonly used in web design, applications, and digital marketing campaigns to draw attention to specific content, features, or to take a desired action. These can be effective to emphasize key content and improve user engagement, and are commonly used across many public library, school library, and corporate or medical library sites. 

In Stacks, a single callout can consist of up to 4 blocks, each block can contain it's own title, image, text, and links to pages or content inside your site or to websites and resources outside of your site. By using the Stacks layout builder you can add one or more callouts to your homepage or other landing pages as needed. 

You can also ensure consistency in branding and your site appearance by further styling callouts to include borders, select from different block content layouts, modify the color of text and/or links, and more.