An object is said to be moving slowly if it covers less distance in a given time.
An object is said to be moving fast if it covers more distance in a given time.
The distance covered by an object in a unit time is defined as speed
The basic unit for time is second, and it can be calculated in minutes and hours, too, depending on the need. The basic unit for distance is metre. So, the unit for speed is metres per second (m/s). Please refer Motion and Time Class 7 Extra Questions for more information.
CBSE Revision Notes 