These are pronunciation rules and exceptions lists for each language.

use:
  speak --compile=<voicename>

to compile the data files for each language in espeak-data (eg. en_dict).

An "_extra" file, (eg. en_extra) can be used to in addition to the "_list" file to add exception words without disturbing the official "_list" file.  It is treated as an extension of the "_list" file.
