Screencapture app - what is it called

When you create a screen capture and double click on the screen capture it opens the screen capture in a kind of app, that has no name, or presence. It allows you to mark up the image, but the window behaves in a delinquent way. It does not go to back when you click another window, it has no printing resource, and it built in one of those stubborn windows that you can never seem seem to pick up. What is that app thing called? What actually is it?