ELI5 QR Codes - how do they work even with portions covered or obscured?

ELI5 Explain Like I'm 5: Bite sized answers to stuff you should know about - in a mini podcast

How are QR Codes better than regular barcodes? How do they work? The fourth corner square is kinda important - what kind of processing is going on for a QR code to be decoded? Why is error correction so important in QR codes?

... we explain like I'm five

Thank you to the r/explainlikeimfive community and in particular the following users whose questions and comments formed the basis of this discussion: puppett_master, berael, middlefingerin, jagedmetalos, superpansy, simbonegtp and jcdu

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