Decimal is a way of writing numbers where each digit represents the different power of 10 .It also needs a decimal point (dot) to separate the integral and fractional parts of a number.
Each place value is divided by 10 when you move right from the decimal point.
The decimal point separates the whole number on the left from its fractional part on the right. Decimal point serves as a separator between a unit and a part of a unit.
Learn how to convert decimal to fraction here.