https://en.m.wikipedia.org/wiki/Dictionary_coder https://en.m.wikipedia.org/wiki/Dictionary_coder (and an arbitrary large number of other explanations that you

https://en.m.wikipedia.org/wiki/Dictionary_coder https://en.m.wikipedia.org/wiki/Dictionary_coder (and an arbitrary large number of other explanations that you can find with a search) In a nutshell, both encoding and deciding side hold a dictionary that maps long sequences of data to still-unique short ones and vice versa (ie. a bijective mapping). Encoder uses it to compress, decoder reverses it. There are obviously many interesting practical questions such as how the dictionary is synchronized, how the mappings are determined, how to keep it a bijective function, etc.