1. How Fast Some liquids flow easier than others.
The measurement of how fast a fluid runs
is called the flow rate.
Flow rate is a good indicator of viscosity.

2. Viscosity Viscosity can be described as the resistance to flow.
Liquids with a high viscosity have a low flow rate. (molasses)
Liquids with a low viscosity have a high flow rate. (apple juice)

3. Viscosity
Viscosity is important in many situations. For example, in cold winter weather, you would choose a motor oil with a low viscosity for your car.
Why is this? As liquids are cooled their viscosity increases. A more viscous oil would not move as freely to lubricate engine parts.