ℚ represents the set of all rational numbers in mathematics. Rational numbers are numbers that can be expressed as the fraction of two integers, where the denominator is not zero. This includes whole numbers, fractions, and finite or repeating decimals. The symbol ℚ is derived from the word "quotient," reflecting the idea that rational numbers can be formed by dividing one integer by another. Examples of rational numbers include 1/2, 3, and 0.75. The set ℚ is a fundamental concept in number theory and is essential for understanding more complex mathematical ideas.