The world leaders get together to discuss the most important financial and economic issues of the day. Members then try to make sure that their plans are co-ordinated. It's expected that trade, climate change and the crisis in relations with Iran will be big topics this year.
Leaders also have many important talks on the side-lines of the summit. There is a lot of interest in who US President Donald Trump is meeting up with. Separate talks are set to take place between Mr Trump and Chinese President Xi Jinping; and between Mr Trump and Indian prime minister Narendra Modi to talk about tariffs - extra taxes on imports and exports.