Square numbers are numbers that result from multiplying two equal factors. They can be represented visually as squares, with the factors as the length of the sides. Some examples of square numbers are 1, 4, 9, 16, 25, 36, 49, 64, 81, and 100. An exercise identifies which numbers in a figure are square numbers, with the correct answers highlighted in blue. The document provides definitions and examples to explain what square numbers are.