Ask a development expert: What should international aid be used for?
Then prepare yourself to be bombarded by a list of priorities, trade-offs and competing demands — not to mention reasons why this is too simplistic a question to ask anyway, and that we need to understand the context, politics, economics, effectiveness and many other factors before even beginning to think about how to answer it.
Ask the average person on the street the same question and they might say something along the lines of “ending poverty and meeting basic needs.”