Different IDs provided by Shopify

Shopify provides different IDs that form the final order, starting from:
a) orderId - this is the Shopify backend order number. This is Shopify's unique identifier that appears in the admin URL of an order. Example:
b) productId - ID of a product that can have multiple variants (see below)
c) variantId - the ID of the given variant of a certain product
d) inventoryItemId - each of the variants can be stocked at a different location, which brings us to this metric