A Microsofty going by the name Planky has generously posted a cartoon video explaining the ideas that are central to modern cryptography. It covers encryption, certificates, public/private key and digital signatures and all in a way that you can understand.  

If you don't believe me just watch, but be warned it is 30 minutes long and you will probably not want to get up and do anything else until it is finished:

 If this made you think that cryptography was mathematically within your grasp, check out Planky's earlier excellent article on the same subject - Crypto Primer: Understanding encryption, public/private key, signatures and certificates - it has the advantage that you can read it at your own pace and think about the deeper parts.