i'm not sure if this question is in the right 
section. its not from a textbook, it is from an algebra II honors summer packet.

it says:
name the sets of numbers to which each number belongs.
use N, W, Z, Q, I, or R.

and the numbers are:
-1/3,     sqrt5,   and pi.

to me it is very vague, but that is all the information i was given.
maybe the letters have a specific meaning that i was never taught. 
any help at all would be greatly appreciated.

N is for "Natural numbers".  It is the set of numbers used to count with

N = {1, 2, 3, 4, ... }

W is for "Whole numbers".  In addition to the natural numbers, W also
contains 0.

W = {0, 1, 2, 3, 4, ... }

Z is the set of all integers, positive, negative and 0

Z = {..., -4, -3, -2, -1, 0, 1, 2, 3, 4, ...}

Q stands for "Quotients of integers" which means the set of rational numbers

I stands for "Irrational numbers" which means all real numbers which are
not rational numbers, i.e cannot be written as the quotient of two integers.

R stands for "Real numbers" which includes all the above.

-1/3 is the Quotient of two integers -1, and 3, so it is a rational number and
a member of Q. -1/3 is also, of course, a member of R.
 _
Ö5 and p are irrational because they cannot be writen as the quotient of 
two integers.  They both belong to I and of course R.

Edwin