Float and Real data Type

What is meant by float and real data type?? plz give example for better understanding my 2nd que is that for number which data type we use in SQL statement.

Both real and fload data types are approximate data types. Real data type uses 4 bytes for storage and has a precision of 7 digits. But float uses 8 bytes for storage and has a precision of 15 digits.
When you are trying to select the numeric data type to use, your decision should be based on the maximum range of possible values that you want to store, and the precision and scale that you need.