The Forum's special ability gives +15% to "Bonus Production Yield". The District upgrade to the Hearth gives +10% to "Global Extra Production Chance". The Without Restrictions cornerstone text says that it gives "10% bonus yields from production". Well-Rested Workers cornerstone says it gives workers "a +20% chance of doubling their yields".
It's not clear if all of these are the same thing, whether they apply to camps/farms/mines or just industry buildings, whether they influence bonus resources from harvesting nodes (like trees), and so on. A single term and tooltip would be helpful.
Near as I can tell they are indeed all the same thing and stack together and affect everything from gathering to harvesting to production (except for effects like the farmers with biscuits cornerstone, which specifies it).