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

Explanation: Let us discuss decimal.
A number whose decimal part and whole number part are separated by a point is called decimal.

For example, \$365.143\$.
Here, \$365\$ and \$143\$ are separated by a point. So, \$365.143\$ is a decimal number.

Subtracting decimals means finding the difference between decimal numbers.

Explanation: In this image we are subtracting two decimal numbers \$48.5\$ from \$23.4\$ we get \$25.1\$.