Earlier quoted context omitted.
How well do you understand the term "homomorphism"? Search engines are the most common example, in general.
Just to be clear, you're referring to coding theory ( https://en.wikipedia.org/wiki/Coding_theory ) in the sense of geometric codes from information theory, right? I fail to see an obvious way search engines fit in.
Coding theory is the matrix algebra of information theory.
You should understand the meaning of the word "homomorphism" as it is used in Multilinear Algebra before you read about how search engines score results in an unbiased manner.
This is not the type of thing you can read by haphazardly browsing wikipedia. Believe you me that I have tried inasmuch. You need to buy books, read journal articles, and then learn through a graduate level math course.
The best advice I can give you is to read about how search engines calculate "hits", and to search through scholar.google.com before you check wikipedia.org!