Policies are a way to change the region's functionality, whether that be through speeding up research times, new grants, or making items cheaper.
To add a policy, type in: $$addpolicy <policy>
To remove it, type in: $$removepolicy <policy>
A policy can't have it's added/removed state changed more than once a day.
Here is the list of policies:
Solar subsidies -10% solar power plant build price, -10% energy price
Public logistics access All corporations can export and buy assets as if they had an additional logistics center in this region (this does not affect market access), +10% to all facilities' build price
Regional planning -25% to all facilities' build price, +5% to land price
Tourism campaign -4s to airport production time (but never less than 0:30), airports require an additional 4x of jet fuel
Low income tax +2 Happiness in a region
Research grant -10:00 research time, +10% energy price
Organic farming +10% to Soil health, +10% to all farms' build price
High income tax -5 Happiness in a region, +5 Funding points
Land grant -5% to land price, +25% to all facilities' build price