Shutter speed refers to the duration that the camera's shutter is open and light hits the image sensor to create a photo. The longer the shutter speed, the more light will hit the sensor, resulting in a brighter image. Conversely, a shorter shutter speed means less light will hit the sensor, leading to a darker image.

Shutter speed is measured in seconds, milliseconds, or even fractions of a second and can vary depending on the camera and settings. It can be set manually or automatically, depending on the type of photo you want to take.

A long shutter speed is often used to create motion blur, such as when photographing waterfalls or traffic lights at night. A short shutter speed, on the other hand, can be useful for capturing fast movements or quick action shots. It is important to choose the shutter speed carefully to achieve the desired result and ensure that the photo is well-exposed.