A decimal number can be defined as a number whose whole number part and the fractional part is separated by a decimal point.

The dot in a decimal number is called a decimal point.

Explanation: For example, \$30.9\$.
Here, \$30\$ and \$9\$ are separated by a point. So, \$30.9\$ is a decimal number.

Decimals that have the same number of digits to the right of the decimal point are referred to as like decimals..

Explanation: For example, \$40.2\$ and \$39.9\$, in \$40.2\$ and \$39.9\$, there is only one decimal place after the decimal point, so \$40.2\$ and \$39.9\$ are like decimals.