A super-noob in encoding, right here. I downloaded a Wii ROM of Super Mario All Stars - It was another game though - that was just 18MB and when I extracted the .rar file, I found a functioning .iso of 4.5GB.

I'm really invested into knowing what makes this kind of compression methods possible? It's fascinating. Now I a little about how their file type is much more important issue, But can anyone give me a simplified explanation about this?

Here is a picture:

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