Well, you pay 20k bells to introduce a certain rule to your town that will benefit you. There are four Ordinances available:
~ Beautiful Town keeps flowers from wilting, and slows the growth rate of weeds.
~ Bell Boom makes items sell for more, but also inflates the buy price of items.
~ Early Bird makes residents, shops, etc. open/wake up earlier.
~ Night Owl makes residents, shops, etc. close/go to sleep later.
Ordinances can be cancelled for free, if you wish to change them. Only one Ordinance can be in use at a time.
Is that any help? xD