Web templates in Microsoft Power Pages are essential for creating and managing the layout and content of your web pages. Here are some key points about them:

1. Definition: A web template is a metadata record used to store template source content. It typically contains Liquid code for dynamic content rendering.
2. Usage: Web templates can be used to create custom page layouts, headers, and footers for your Power Pages site. They can be included in other content or combined with other templates using template tags.
3. Attributes: Each web template has attributes like Name, Source (the template’s content), and MIME Type (optional, for specifying the content type).
4. Custom Page Layouts: You can use web templates with page templates to create new custom page layouts. This allows for flexibility in designing the structure and appearance of your web pages.
5. Components: Web templates can also be used as components, allowing you to build configurable, repeatable elements that can be customized for each specific instance.