Used items that customers have returned to the original manufacturer due to a defect or because they’ve changed their minds. They can also be product demos or items with packaging damaged in handling. To prepare an item for resale, the manufacturer puts it through a detailed refurbishing process to make necessary repairs. This can involve cleaning, running functionality tests and repackaging.
Ashley Donohoe, What is a Certified Refurbished Product?, Techwalla (March 31, 2015), https://www.techwalla.com/articles/what-is-a-certified-refurbished-product
See also refurbishing