Can't remember definition of $\lvert G \rvert_{p'}$

Question

For $G$ a finite group, I know that $\lvert G\rvert$ denotes the order of the group. My question is: What is $\lvert G\rvert_{p'}$? Also is this the same as $\lvert G\rvert_p$ (without the prime on the $p$)?

(Sorry for asking such a basic question, but I didn't know how to Google it).

Answer 1

As mt_ says, $|G| = |G|_p \cdot |G|_{p'}$ with $|G|_p$ a power of $p$ and $|G|_{p'}$ relatively prime to $p$.