Host reporting is available for tests that have been enabled to capture host data in the advanced section of test properties. It provides performance data for specific hosts across your test runs.
The component timings (DNS, Connect, Wait, Load, Response) are the sum of all requests on the page. So, if there are two requests to a particular host with Connect time of 100ms, then the Connect time for the host will be 200ms. This is done to avoid "averages of averages" when looking across multiple test runs.
Webpage Response, on the other hand, measures the time during the webpage load that we were performing network connections to the host. It will not include gaps or time during the page load that the client is not communicating with the host. It also is de-duplicated (in that overlapping requests are not double-counted).