Deck W stands for West Deck, a floor/field seating section located in front of Section 138 for many concerts at Soldier Field. Seats in the West Deck (as well as the East Deck on the opposite side of the field), are generally reserved as field level handicap accessible seating sections.

Deck W Seating Location at Soldier Field
West Deck seats are located on the field level (near the west sideline) and are most frequently reserved for handicap accessible seating