A complex type that specifies the headers that you want CloudFront to forward to the origin for this cache behavior. For the headers that you specify, CloudFront also caches separate versions of a given object based on the header values in viewer requests; this is known as varying on headers. For example, suppose viewer requests for logo.jpg contain a custom Product header that has a value of either Acme or Apex, and you configure CloudFront to vary on the Product header. CloudFront forwards the Product header to the origin and caches the response from the origin once for each header value.