A fraction is a mathematical representation of a part of a whole. It consists of two numbers separated by a horizontal line, called the fraction bar. The number above the fraction bar is called the numerator, and the number below the fraction bar is called the denominator. The numerator represents the number of parts being considered, while the denominator represents the total number of equal parts that make up the whole. Fractions can be used to express values that are not whole numbers, such as 1/2, 3/4, or 5/8. They are an essential concept in mathematics, used in various operations like addition, subtraction, multiplication, and division.