I’m troubleshooting an issue with permalinks. As part of my troubleshooting, I discovered that this row in the table wp_options is changing:

+-----------+---------------+----------------+----------+
| option_id | option_name   | option_value   | autoload |
+-----------+---------------+----------------+----------+
|   1725617 | rewrite_rules | a:323:{...}    | yes      |
+-----------+---------------+----------------+----------+

(I put ... in the value of the third field for brevity.)

What does the rewrite_rules option do? When is it used? How is it modified? What could modify it? Is there any documentation for this option? I haven’t found documentation for it, yet.