The expression 10 % 3 evaluates to 1. The % operator (modulus) returns the remainder of a division operation. When 10 is divided by 3, the quotient is 3 with a remainder of 1. The modulus operator is often used to check if a number is even or odd (n % 2 === 0 means n is even), to cycle through a range of values (like in circular arrays), or to ensure a value stays within a specific range.