The modulus operation, often represented by the symbol %, calculates the remainder of a division between two numbers. For example, in the expression 7 % 3, the result is 1 because when 7 is divided by 3, it goes 2 times with a remainder of 1. This operation is useful in various fields, including computer science and mathematics, for tasks like determining even or odd numbers. In programming, the modulus operation helps in tasks such as looping through arrays or checking divisibility. For instance, using i % 2 can determine if a number i is even (result is 0) or odd (result is 1). This simple yet powerful operation is fundamental in algorithms and data structures.