You put an offer on a new house that says, "I will buy this, but only if my current house sells by X date." In a competitive market, sellers often reject these offers in favor of "cleaner" ones.
Your real estate agent will try to schedule both "closings" on the same day (or back-to-back) to minimize the time you're "homeless" or paying double. buying a house while selling another
A short-term loan that uses the equity in your current home to provide the down payment for the next one. It "bridges" the gap until your first home sells. You put an offer on a new house
Don't just get pre-qualified; get a full pre-approval so you can act fast when you find a house. "I will buy this