An excellent discussion from 2012: https://news.ycombinator.com/item?id=4342991

If I have understood this correctly - can I equate the underlying principle of this "possibility of more efficient error correction" to spotting a typo in a text? That as words grow to sentences, to paragraphs on specific topics and so on, it becomes easier to guess from context which word should have been written, when a letter is written incorrectly?

The Shannon limit is simply a number: ln(2) or in decibels approximately -1.59 dB.