This is one of 3blue1brown’s explainer videos which I have featured here previously. This one tackles the basic ideas behind cryptocurrencies and how they secured by cryptography.
It may not be clear to you, as it wasn’t to me, just how hard it is to break SHA256 cryptography or exactly how unlikely it is that anyone could break the code.
You will certainly have a better understanding having seen this video, which is just one of a series of explainer’s about maths in general and occasionally cryptocurrencies.
You can watch more videos in a similar vein on 3blue1brown’s youtube channel.