These are the two most common measurements:
Milliliters
A milliliter (that is "milli" and "liter" put together) is a very small amount of liquid.
Here is a milliliter of milk in a teaspoon.
It doesn't even fill the teaspoon!
If you collect about 20 drops of water, you will have 1 milliliter
20 drops = 1 milliliter
And a teaspoon can hold about five milliliters:
1 teaspoon of liquid is about 5 milliliters
Milliliters are often written as ml (for short), so "100 ml" means "100 milliliters".
********************************************
Liters
A liter is just a bunch of milliliters put all together. In fact, 1000 milliliters makes up 1 liter.
1 liter = 1,000 milliliters
This jug has exactly 1 liter of water in it.
Liters are often written as L (for short), so "3 L" means "3 Liters".