The expression "7 mod 5 = 2" refers to the mathematical operation known as the modulus. In this case, it means that when you divide 7 by 5, the remainder is 2. The modulus operation focuses on what is left over after division, rather than the quotient. To visualize this, if you divide 7 into groups of 5, you can form one complete group, which uses up 5. This leaves you with 2 remaining. Therefore, the result of "7 mod 5" is 2, indicating the leftover amount after grouping.