You activated by mistake an advanced view mode. You can switch between view modes by pressing "info" (or maybe "display" for you) when in view mode.

The view switchs in that order (sorry for image quality) :

1. Classical View : your photo and some settings and nothing else

2. Classical View with more information : your photo, some settings image quality (JPG/RAW) and pictures number (xx/yy)

3. First Advanced View : image in the top-left corner, histogram on the top-right and settings information in the bottom

4. Second Advanced View : image in the top-left corner, color histogram in the top right, classic histogram in the bottom-right, some information in the bottom-left.

It's probably a good thing that you stumbled into this "problem". The advanced views are really helpful, especially histograms. Take a look here : How and why do you use an image histogram?

If you don't know about these options, you might want to know about "highlight warning" too and active it. With this possibility, the over-exposed areas (the ones completely white because your sensor received to much light = bad exposition) are blinking. It's really helpful and you probably want to activate it :)

If you don't know how to activate highlight warning, take a look here : 700D how to blink on over-exposure?