Can you please explain Exposure to me?

I took several photos in the snow and the exposure adjusted appropriately. I practiced inside and got this. I'm so confused. Is this accounted to the light emitting from outside into a darker room? And please explain this to me like you're talking to an elementary school student. I mean, really put it into laymen's terms. Visuals and demonstrations always help.

Here are my photos:
https://goo.gl/LHnH6m
https://goo.gl/VuXZyj
https://goo.gl/fvhvsC

Camera: Nikon D3200
Manual setting
Regular lens

And before you suggest adjusting my settings, I know how to adjust settings. I'd like an explanation on how Exposure works!

In the photo with Exposure +5, the meter is reading that the light is low-- so the window light is bright, the exposure is high, the image comes out bright, but the meter is reading that the light is low. Does a higher Exposure necessarily mean that the image will be brighter? It seems more logical for the meter to read on the brighter scale if the camera is producing a bright photo with high Exposure.

With -5 Exposure, how is the meter registering to the light of the window but producing a dark photo? Why is that?

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