1. The problem is to understand what $\pi$ (pi) is. 2. $\pi$ is a mathematical constant that represents the ratio of a circle's circumference to its diameter. 3. This means if you measure the distance around a circle (circumference) and divide it by the distance across the circle through its center (diameter), you always get the same number, which is $\pi$. 4. The value of $\pi$ is approximately $3.14159$, but it is an irrational number, meaning it has an infinite number of decimal places without repeating. 5. $\pi$ is used in many formulas involving circles and spheres, such as the area of a circle $A = \pi r^2$ and the volume of a sphere $V = \frac{4}{3} \pi r^3$. 6. In summary, $\pi$ is a fundamental constant in mathematics related to circles and appears in various areas of science and engineering.