An Ask is a listing StockX sellers create for their item, designating a specific amount of money that they are willing to sell their item for.
It tells the world, “What up world. If you want to buy these shoes or this watch at this price, I’ll sell ‘em. In fact, I’m so serious about this sale life that I’ve linked my Paypal or bank account to this Ask so that we can make this move happen faster than a Yeezy drop sell out.”
If someone puts out a lower ask than you, no worries. If an ask matches their (now lowest) ask, they’ll get the sale. But your ask is still active and could be accepted if it becomes the lowest ask again.