A perfect square is a number that can be expressed as the product of an integer multiplied by itself. For example, 1, 4, 9, and 16 are perfect squares because they can be written as 1x1, 2x2, 3x3, and 4x4, respectively. Perfect squares are always non-negative and can be found by squaring whole numbers. Perfect squares have various applications in mathematics, including geometry and algebra. They are often used in solving equations and can help in factoring expressions. The sequence of perfect squares continues indefinitely, with each new perfect square being the square of the next integer, such as 25 (5x5) and 36 (6x6).