Real numbers are a type of number that can be used to measure a continuous one-dimensional quantity such as distance, duration, or temperature. They can be found in the real world and include whole numbers, rational numbers, and irrational numbers. Here are some key points about real numbers:

• Real numbers can be positive, negative, or zero.
• The set of real numbers is denoted by R or and is sometimes called "the reals".
• Real numbers include rational numbers, such as the integer -5 and the fraction 4/3, and irrational numbers, such as pi and the square root of 2.
• Real numbers can be represented on a number line, where positive numbers are to the right of zero and negative numbers are to the left.
• Imaginary numbers, such as the square root of -1, are not real numbers.

Real numbers are used in many areas of mathematics and science, including calculus, physics, and engineering. They are an important concept to understand in order to solve mathematical problems and make accurate measurements in the real world.