Grade A is the very best quality that you could expect from a MacBook or iPhone. Grade A devices are in near-mint condition. Their cosmetic aspect is excellent and they show next to no signs of previous use.
With a Grade A phone, you will see very minimal amounts of scuffing on the case. A Grade A laptop will look (almost) like new, with very minimal amounts of scuffing and marks and the lid, keyboard and other areas of its design. Grade A devices will likely show typical signs of light usage (e.g. slight marks on the keys) but you shouldn’t expect to see any scratches, chips or significant blemishes.