A secondhand or used goods simply mean it is no longer in the same condition as it was when transferred to the current owner. When the term used means that an item has expended its purpose it is typically called garbage, instead.
Governments require some used goods to be sold through regulated markets, as in the case of items which have safety and legal issues, such as used firearms or cars. For these items, government licensing bodies require certification and registration of the sale, to prevent the sale of stolen, unregistered, or unsafe goods.
Second-hand goods are generally presented for sale in a good state of repair and cleanliness, but should be thoroughly cleaned before use.
No doubt it is more preferable to get a new product than a used ones in terms of risk depending on the type of products been purchased.