wooden_flower Volunteer Community Mentor.
Power on means just that - the item accepts power. It is not an indication of functionality. It usually means the seller is not able to test the functionality.
If you are looking to buy an item, look at the item condition. If it is new or used, then it means that the item works as intended. But - many sellers do not understand this. It does mean if the item does not work that you can return it at the seller's expense, but do you want that hassle?
