Real variables are quantities that can take on any value within a continuous range, typically represented by the set of real numbers. They are used in mathematics and statistics to model and analyze various phenomena, such as time, distance, and temperature. Real variables can be positive, negative, or zero, and they can be expressed in decimal or fractional form. In mathematical functions, real variables often serve as inputs that produce corresponding outputs. For example, in the function f(x) = x^2, x is a real variable that can take any real number, and the output will always be a non-negative real number. This flexibility makes real variables essential in calculus and other areas of mathematics.