Refurbished Grade B is the second-best quality you can expect from a refurbished device. Refurbished Grade B products feature some light scratches or scuffs. Bear in mind this is only a cosmetic condition difference with Grade A devices; Grade B laptops and phones are tested thoroughly and are perfectly functional.
Because of these small signs of use, Grade B products are more affordable than refurbished Grade A devices. Something to keep in mind if your budget is restricted.