在Django,什么是sku?

当我阅读django代码时,我经常在模型中看到所谓的“sku”,以及 "slug" . 例如:

name = models.CharField(_("Full Name"), max_length=255, blank=False,
    help_text=_("This is what the product will be called in the default site language.  To add non-default translations, use the Product Translation section below."))
slug = models.SlugField(_("Slug Name"), blank=True,
    help_text=_("Used for URLs, auto-generated from name if blank"), max_length=255)
sku = models.CharField(_("SKU"), max_length=255, blank=True, null=True,
    help_text=_("Defaults to slug if left blank"))

我不确定与slug URL的关系。

如何以及何时使用此SKU?