The document discusses squares and square roots. It defines a square number as a number multiplied by itself. It provides examples of perfect square numbers and their properties, such as being even or odd and having an even number of zeros at the end. The document also discusses finding the square root as the inverse of squaring a number using prime factorization or long division. Pythagorean triplets are introduced as sets of numbers that satisfy the Pythagorean theorem for a right triangle. In conclusion, the key properties of square numbers are that they end in 0, 1, 4, 5, 6, or 9 and have an even number of zeros at the end.