The previous chapter opened the door to side effects, including, among others, saving data from your Haskell application on disk or sending it through the network. However, the only true serialization mechanism that was introduced was the binary one, through the binary package.
In many cases, a textual representation of data is preferable to a binary one. Even though it is usually much larger, data encoded in text is more readable for a human consumer, making your programs much easier to inspect and ...