Shutter speed is the amount of time your camera’s shutter stays open when you take a photo. It controls two things: motion and brightness. A fast shutter speed (like 1/500 or 1/1000) freezes movement—great for birds, sports, or kids. A slow shutter speed (like 1/30, 1/10, or 1 second) lets motion blur—useful for silky waterfalls, light trails, or creative blur.
It also affects exposure: slower shutter speeds let in more light and make the photo brighter; faster shutter speeds let in less light and make the photo darker.
Handheld rule of thumb: use about 1 divided by your focal length (50mm ≈ 1/50, 200mm ≈ 1/200) to avoid camera shake, unless you have stabilization.