What does Romans 2:14-16 refer to?

Dusty, Romans 2:14-16 is reiterating the truth that the natural law is written on the heart of all men, so that all men know that certain things are against God’s law and that certain things are in accordance with the natural law of charity, etc.  As the Haydock Bible and Commentary correctly explains about this verse,

“these men are a law to themselves, and have it written in their hearts, as to the existence of a God, and their reason tells them, that many sins are unlawful: they may also do some actions that are morally good, as by giving alms to relieve the poor, honoring their parents, etc. not that these actions, morally good, will suffice for their justification of themselves, or make them deserve a supernatural reward in the kingdom of heaven; but God, out of His infinite mercy, will give them some supernatural graces” which if they continue to cooperate with they will get more graces and eventually be exposed to the Catholic Faith, which they must have to be saved.