See 101 - Cookbook for a complete discussion of working the cookbook.
The all.macro file residues in the Foldit installation directory, for example c:\Foldit.
The all.macro file is digitally signed. Only the Foldit client can add, change, or delete cookbook recipes.
Players using multiple Foldit clients can copy all.macro from one installation to another, avoiding the need to download the same recipes multiple times.
While all.macro can only be changed by the Foldit client, the contents are not encrypted, and can be viewed in a text editor. The format of all.macro is a properties file, consisting of keyword-value pairs. Other Foldit properties files, such as options.txt, use a similar format.
For all.macro, the keyword portion consists of "_recipe_*nnnnn*", where *nnnnn* is the "node number" of the recipe on the fold.it website. The value portion consists of the recipe contents and related information, such as the cookbook folder the recipe is stored in.