The remainder operators
In mathematics, the remainder is the amount "left over" after performing some computation.
For example, the remainder of 5 / 3 is 2.
Many programming languages use the percentage sign (%) as an operator to calculate the remainder.
For example:
5 % 3 == 2
Remainders can often be calculated on both integers and floating point numbers. For example,
5.3 % 3 == 2.3
When working with negative numbers, the result always has the same sign as the dividend (the number on the left hand side that is being divided). For example:
-5 % 3 == -2
5 % -3 == 2
-5 % -3 == -2
Some languages (such as Python) use the % operator for the calculating the modulus, not the remainder.
This treats negative numbers differently.
You can learn more about this on Wikipedia.