If two cells match, return value from third

Question

Here\'s a simple explanation of what I\'m having trouble with.

Column A: List of 2300 order numbers
Column B: Email Address associated with an order number
C

Answer 1

I think what you want is something like:

=INDEX(B:B,MATCH(C2,A:A,0))  

I should mention that MATCH checks the position at which the value can be found within A:A (given the 0, or FALSE, parameter, it looks only for an exact match and given its nature, only the first instance found) then INDEX returns the value at that position within B:B.