Sure,

people post their sales of btc and highlight acceptable payment options. you pick which buy you want. once picked, you lock a small amt of btc as a temporary bond with robosats. seller of btc then locks in the total amount of sale eith robosats. you and your peer then enter a private chat channel in robosats, where they provide details of how you send them money. once youve sent, peer then confirms in robosats they received, and the btc is unlocked to be sent to you.