# How do I break down the math symbols in this equation

$$\frac{n}{\phi(n)}=\frac{n}{n\prod_{p|n}\left(1-\frac{1}{p}\right)}=\frac{1}{\prod_{p|n}\left(1-\frac{1}{p}\right)}$$

How do I learn to understand these equations by myself as I can't seem to find the mathematical notation descriptions online?

The big pi, $$\prod$$ denotes a product. The subscript on this tells you which numbers this product is over. In this example, the subscript says $$p|n$$ which means "$$p$$ divides $$n$$" i.e. the product is over all the prime numbers $$p$$ that divide $$n$$ (the prime factors of $$n$$). $$\phi(n)$$ denotes the Euler-Totient function. This counts the number of integers $$m which are co-prime to $$n$$, i.e. have $$\gcd(m,n)=1$$.
As an example, say we have $$n=105=3\times5\times7$$. Then $$\prod_{p|n}\left(1-\frac1p\right)=\left(1-\frac13\right)\times\left(1-\frac15\right)\times\left(1-\frac17\right)=\frac{16}{35}$$