Radicals are numbers that involve roots, such as square roots or cube roots. For example, the square root of 4 is written as √4, which equals 2. Radicals can also represent irrational numbers, like √2, which cannot be expressed as a simple fraction. In mathematics, radicals can be simplified by finding perfect squares or cubes within the number. For instance, √8 can be simplified to 2√2 because 8 is 4 times 2, and the square root of 4 is 2. Understanding radicals is essential for solving various mathematical problems, especially in algebra.