The promotion is available when ordering through the Wingstop website or mobile app on Tuesdays and applies only to two Crispy Tenders in a single flavor. Dip is not included.
According to the fine print, "Prices may be higher in Alaska, California, and Hawaii." It's a 2-for-$3 deal here in Los Angeles.
For comparison, my local Wingstop does not normally sell two Crispy Tenders online but does regularly offer four Crispy Tenders and a dip for $8.39. There's also an option to get two additional tenders for an extra $2.49.
Photo via Wingstop.