The basic idea is that you upload data that you have collected. It assumes that you have got a file of organised data, that you have analysed, but you feel that others may benefit from using it as a standard, or just to get ideas, or to do further work on it e.g., make a comparison with your their country's data.
In theory it should be a table, a spreadsheet or a database. In practice, I see RGers putting any old document up, even papers (by accident).