Most marketplaces want products on a plain background, and a photo taken on your kitchen table is not that. Cutting the object out is the fix.
Erase background is a manual brush tool, not an automatic product detector. It saves a transparent PNG; it has no background-colour picker or direct JPG output. Conversion to JPG is the separate step that supplies white behind transparent pixels.
Illustrative example: cut a dark bottle away from a contrasting tabletop, restore any accidental brush marks on its label, then convert the PNG to JPG. Check at normal display size that the label is readable and the bottle edge has not been removed.
Fine hair, translucent glass and mesh need care and may not produce convincing edges. The working-resolution reduction can affect a large original. Check the marketplace's actual requirements rather than assuming a white backdrop guarantees acceptance.
The cut-out is saved as a PNG with a transparent background. To turn it into a photo on plain white, run it through Convert format and choose JPG. A JPG cannot be transparent, so the see-through areas are filled with white, and you have the classic product shot.
Photograph the product against a plain, evenly lit surface in the first place, because the cleaner the original, the less time you spend erasing. Take care near the edges, and use Put it back to restore anything you took away by mistake before you convert.
No. You paint manually with Erase and Restore, with Undo available.
Yes. Keep the cutout PNG; the JPG conversion intentionally replaces transparent regions with white.
Convert the cut-out PNG to JPG with Convert format. The transparent areas are filled with white automatically.