A header is a section title to represent the entire contents of the section.
There are two types of headers for tablet and one type for mobile.
A. Caption Header
Represent the contents of the section. It uses a simple and easy word or phrase to understand the purpose of the section.
B. Data Table Header (Tablet only)
A Data Table Header is specifically used for Data Table view. It always stays right below the app bar when scrolling down through the Data Table contents.
Headers are not shipped with the SDK yet, but will be implemented in the future.