Confusion regarding symbol

Hey guys , i am unclear regarding a symbol which i encountered in my work. I was given a question in which they state a few algorithm. The part which i am confused about is when they told me to use a variable named q where q|P -1 . P is also a variable , but a prime number.

What i am confused about is what does "|" mean?

1) Does it mean that q = P -1 , which means to say if P is 11 , q is 10?

2) Does it mean that q can be any number which is less then P -1 ? If P = 11 , then q can be from 1 till 10.

Or am i completely wrong in understanding what "|" does? Hope for some clarification. Thank you.