Shutter speed represents the length of time in seconds that the camera's shutter was open while taking a photo.
For shutter speeds of less than 1 second, they are usually represented as a fraction. For example, 1/200 means that the shutter was open for one two hundredths of a second.
Shutter speeds of longer than 1 second are represented by whole numbers. For example 1 second, 23 seconds. Extremely long shutter speeds are sometimes represented in minutes and seconds. 1min 35sec, etc.
A longer shutter speed means that more light enters the camera during a photographic exposure, therefore making the resulting photo brighter.