Action cameras are small, lightweight, wearable, mountable, portable, and sometimes waterproof camcorders. They're useful because you can mount them to pretty much anything—from skateboards, surfboards, bicycles, and drones, to helmets, body parts, and even your pets. CamerashopUSA has a complete and expanding line of action cameras that will satidy all of your needs.
Action cameras are unlike any other kind of camera. They're designed to be attached to helmets, surfboards, cars and other objects, and they're small, tough and simple, with a lens that captures the world in high-definition video in a wide-angle fish-eye perspective.
Their small size and dramatic POV ('point of view') footage has made them popular with extreme sports personalities who capture their adventures by attaching cameras to themselves or their equipment. They're also used by TV production companies where using a regular video camera would be impossible.
Action cams are almost the opposite of regular video cameras-- they're small, they're inexpensive, they're simple to operate and tough.
GoPro is the market leader with its iconic box-shaped Hero cameras, but action cams also come in a 'bullet' style, like the iON Air Pro. There's lots of choice now, and you shouldn't just buy on brand-- think about what you want from an action camera and how you plan to use it.
If you're helmet mounting, then a bullet cam will probably be the best choice. For a chest mount a box design will be more stable.