The mother of all inequality disputes. (All data are in PPPs and on per capita basis; all measures are in Ginis.)
Unweighted international inequality (aka Concept 1 inequality) is inequality of all countries' GDPs per capita (as simple as that). It has been going down, but slowly, over the past 30 years, that is, countries are more or less income converging.
Population-weighted inequality (aka Concept 2 inequality) is the same as Concept 1 ineq but now each country enters the calculation with its total population. Obviously China, India etc. now count for a lot. That inequality went sharply down in the past 40 years, but has now stalled. This is an important fact b/c Concept 2 inequality is the most important factor in determining what happens to inequality among all 8 billion people in the world.