Introduction should clarify that hashes are used in paths to software

[tejing1]

This section: https://github.com/divnix/nix-book/blob/f6448f447d5584854803ac7829e3dd1c00686a32/src/ch02-00-introduction.md?plain=1#L12-L18 is difficult to follow because no mention has yet been made that hashes are used to determine the paths at which software is installed. Many of the claims in this paragraph don't make sense without that context.

[jonringer]

;( Fair, I'll think about how to word this in a more clear way.

[tejing1]

The first few paragraphs are the hardest to get right, but also the most important. I'm sure it'll take some iterating.

Is it enough to just make it:

This information is aggregated through hashing, and used to determine the software's installation path, allowing nix to describe...