Modulo Operator
Division between two integers doesn't always result in another integer. The division

left a remainder of 4.

"mod" (contained on the image above, very sorry for night mode viewers) _is an operation that returns a remainder of a division. It stands for modulo operator. The division above can be written with modulo operator into

Given integer a and other integers b, k, and m that satisfy

equation above can be written using modulo operator into

Examples :
(v)