In computer science, compression is an indispensible tool. Anyone familiar with .zip files knows what I mean. Interestingly, there are two kids of compression, lossless and lossy. Lossless compression is like .zip compression, you put a file of, say, 100kb in and the end result is a file of, say, 50k. But when you reverse the process, you get back your original 100kb file.
Lossless compression relies on the fact that in real life information contains patterns. Just imagine taking this post and finding the most common used words in it. Then replace the most common word with a the tag “<1>” and the next most common with “<2>”, etc. The end result would generally be a smaller file, yet by replacing “<x>” with the original words you could recover the original file in its entirety.
I used to wonder what possible use lossy compression could ever be. Why in the world would I ever want to save off a compressed version of my files if I couldn’t get them back to their original state ever again?