What does it mean by "Adding Gaussian Noise to a 2D Image"? As far as I understand,

Suppose, we have a 2D image of pixel resolution 200 x 300. That means, the image has 60000 pixels in it.

Now, we would generate $n$ random values and add those values to $n$ number of random pixels.

Now, my question is, what would make those $n$ values to look like Gaussian Random Values?

What would be the logic that I should use?
You can find Gaussian noise generators in many image processing softwares.At each pixel, you add a realization from such random noise generators. You can look for more details at How to Generate White Gaussian Noise. 

On StackExchange, additional sources of information:


Why Gaussian noise is usually used?
Why is Gaussian noise called so?
What's gaussian noise look like?
The model of noise in Image denoising problem