@Ermin Trevisan

I don't understand "the default unit of measure is equivalent of an SKU". Is unit of measure is just a measurement? like kg, litter, cm?

How can this be equivalent of an SKU?

Sorry, I try to explain it better: in Odoo a SKU is a stockable product (variant) with its default UoM. Example: I buy wine in boxes at 6, sell it by the bottle or by the glass and keep inventory in bottles, therefore the SKU is the wine bottle.

And bottle is the default UoM.

@Erime Trevisan hmm... So then what you are saying is that I can specify each product with the UoM as a unique id like White iPhone 6 with UoM "w-iphone6" and Black iPhone 6 with UoM "b-iphone6". Have I got that right?

No. In your example, the UoM is always Unit(s). But you have different products, one product (or SKU in my understanding) is the white iPhone, another one is the black iPhone. If a customer orders a black iPhone, you have to deliver a black iPhone, for that you need to have a black iPhone on stock and in order to have the proper stock, you need to buy black iPhones.The same is valid for white iPhones. In Odoo these are product variants, but each variant is a SKU. In such cases the SKU is evident. In cases where UoMs are different, it is not so evident anymore. Let's take Coca Cola Zero. It is always the same product (it has no different colors, tastes whatsoever, it is Cola Zero). But you may have many different UoMs. Bottles of different sizes, cans, sixpacks, cartons etc.

Easy example: you sell Cola Zero in cans and in sixpacks. In that case it is most probably the best way to define Cola Zero can as the SKU. To do that, you define "can" as the default UoM for Cola Zero.

That was detailed explanation with examples! Thank @ermin Trevisan!!!