This is an indoor estate sale in which the public is invited to shop. Usually the owners no longer reside in the home. The items are organized, tagged with asking price, and set up like a retail store.
This could be a tool sale in a shed where amenities are not available. This type sale requires the knowledge of a liquidator who can price on the spot.
Some companies have multiple contacts who serve various purposes such as preliminary shopping and bulk purchasing. This allows for decluttering the estate and also getting top dollar for selected pieces.
Companies vary with standards and/or policies. However, it is almost essential to list items on social media or online sale sites if the goal is to produce a total liquidation. This is usually done alongside a tag sale.
Bulk buying is almost a necessity in all forms of liquidation. There are plenty items which typically do not sell individually, but bulk it and it will find a new home.
No matter how successful the sale is; there will still be a lot of unwanted items left. Liquidators tend to know bulk buyers who will pay to clean out the remaining items.