What is class y in emirates airline?

Emirates operates a multi-class system, generally First, Business, and economy class seating. Within those parameters are additional fare codes, designed to work within the primary First, Business, Economy model. They can range anywhere from S class to Z class.

In this instance, 'Y' class represents the standard economy cabin. Within that structure a multitude of sub-classes can be represented, covering anything from restricted economy fares, to staff travel codes.