What are "regional" district bonuses?

[steveg700]

I see Nikola Tesla improves a district's regional buildings by +2 hammers, and improves their reach by three tiles. What is this referring to?

 

[Browd]

That refers to Industrial Zones and Entertainment Complexes, both of which have two buildings (Factories and Power Plants and Zoos and Stadiums, respectively) whose bonuses extend to cities within 6 tiles of the district in which they are located. Tesla's bonus allows one such district (the district where he is bulbed) to reach 9 tiles and for that district's buildings to be boosted by +2 production.