This is the mimosa pudica, also known as the sensitive plant, the humble plant, the tickle me plant, and the shame plant. So called because when exposed to stimuli the leaves fold up and droop down.
A lot of things make the leaves fold up: touching them, shaking the plant, depriving the plant of water, and exposing it to chemical or electric stimuli will make them close temporarily. They also close at night and will remain that way until sunrise. We don’t know exactly why they close up. Maybe it has to do with conserving energy, maybe it makes them look less tasty to passing herbivores.
The sensitive plant is native to Brazil but now grows in tropical regions all over the world. It’s been declared an invasive species and a weed in parts of Australia.