The symbol "ℝ" represents the set of all real numbers in mathematics. Real numbers include both rational numbers, like integers and fractions, and irrational numbers, which cannot be expressed as simple fractions, such as π and the square root of 2. This set is fundamental in various fields of mathematics and is used to describe continuous quantities. Real numbers can be plotted on a number line, where each point corresponds to a unique real number. They are essential for various mathematical operations and concepts, including algebra, calculus, and geometry. The real number system is crucial for understanding and solving equations in both pure and applied mathematics.