USB ports are incredibly powerful and useful: they can power speakers and external hard drives, connect to wireless peripherals, and even provide video signals for monitors. Unfortunately, because they’re so powerful they also have some flaws that make them vulnerable to damage. Because USB ports are powered, sticking a metal connector that isn’t a USB jack (your headphones by accident, for example) in one can fry the port. What’s worse, it can actually fry the controller board and take out ALL of your USB ports. USB ports are also very vulnerable to physical damage, mainly because people plug and unplug devices so often that the ports are under a lot of stress.
If your USB port isn’t working: