Humanitarian Aid propagates your country's culture by helping the poor and the opressed in the other Civilizations, which turns out to be a rather good bussiness. A bit like Cleric, she can <l:6,29>Convert Cities<e> so they share your progressive values and become more open to your culture-related merchandise, which redirects some of their money to your Civilization and makes them unwilling to go to war with you. In such <l:6,104>cities<e>, the Humanitarian Aid can perform, well, humanitarian aid (represented by  <l:6,30>Sell Indulgences<e> special action) which boosts locals' <l:6,96>happiness<e>. The latter action is sponsored from your own citizens' personal money, so it's not only free, but leaves a small <l:6,92>Gold<e> surplus in your empire's pocket. Only a handful of <l:6,81>governments<e> can employ this unit, namely <l:7,10>Democracy<e>, <l:7,11>Communism<e>, <l:7,17>Ecotopia<e> and <l:7,21>Virtual Democracy<e>.