This is a constant used when registering the download post type. By defining this constant, and setting it to true you can disable the post type archive for downloads. This is useful for sites where downloads are displayed manually, via short codes or template tags, rather than via default post type archives.
To disable the post type archives, place this in your theme’s functions.php, or any custom plugin:
define('EDD_DISABLE_ARCHIVE', true); // disable download post type archive