system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: what is a sovereign wealth fund(SWF), and how do they work?
gpt
Country has spare money.  Country sets up Sovereign Wealth Fund that uses the spare money to invest in stock markets and such in general, so they can make a profit off of the spare money that government had.  So essentially, it's countries that are investing.