The word nuts has several meanings:

1. Crazy, silly, or out of control. When your little brother is bouncing off the walls with energy, you might say he's acting nuts. If someone comes up with a wild, impractical plan, you could call it a nuts idea. The phrase driving me nuts means something is making you extremely frustrated or annoyed, like when a mosquito keeps buzzing around your head.
2. Hard-shelled seeds or fruits that grow on trees and plants. Walnuts, almonds, and peanuts (though technically legumes) are all considered nuts. Squirrels famously gather and hide nuts to eat during winter. Nuts are packed with protein and healthy fats, making them nutritious snacks. Some people have severe nut allergies and must avoid them completely.
3. Small metal pieces with threading inside that screw onto bolts to hold things together. When you're building something, you twist a nut onto a bolt to fasten parts securely. If a nut comes loose, whatever you built might fall apart. The phrase nuts and bolts refers to the basic, practical details of how something works.