What it means
ACV (Actual Cash Value) is the value an insurer uses to settle a claim: what the car was worth on the market right before the damage, taking age, mileage and condition into account. IAAI shows an ACV on its lots; Copart shows its own Est. Retail Value.
What it means for a buyer
ACV is a reference, not a price you will pay or get. Use it to judge how much of the car's value the damage represents, together with the repair cost estimate.