what is the use of `decimal` and `numeric` datatype in postgreSQL. As per the reference the following is the explanation given to these datatypes. 

```
Decimal,numeric --> It is a user specified precision, exact and range up to 131072 digits before the decimal point and up to 16383 digits after the decimal point.

```

The above statement shows the description of `decimal` and `numeric` datatype. But, still I didn't understand what is the
 exact use of these data type and where it is used instead of other datatypes. 

Answer with example is much appreciated...