The basic functionality of this control is to use it as a loader while loading image in image control. It can also be used for making user understand that some long background task is in progress. When we give a web source to image control it takes some time to download the image from the web and display it in the image control. The download and display takes considerate amount of time which depends on the conncectivity strength. So to make user understand that some process is going on in background we can show loader over the image control till then and as soon as original image gets downloaded and displayed loader is overlapped by original image. Similar kind of scenario  we can show loader for long running background tasks.