See a bit in the canvas inspector that this is “screen space overlay”?
It means:
" This rendering mode places the user interface elements on the screen displayed on top of the scene. "
And what that means is that you don’t have to worry about where Canvas and child text appears on the scene screen. When you start the game, the user interface elements will be superimposed on the background background objects, and everything will be fine.
Source: http://docs.unity3d.com/Manual/UICanvas.html
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