SKU when selling?

[Usive]

How  do I find out what I need to put as my items SKU when posting a product on the market?

[Claireschen Hesten]

the SKU stands for stock keeping unit you don't need to fill this in you can leave it blank

[Dazler]

This field allows you to add a "code" which may make your role as a merchant easier. It is an optional field and so you are free to leave it empty. If you are a very organised person, you may want to add some code (such as BC1 for "black coat sized as small") so that when you work with your listings in the future, it is quicker and easier to locate items. Most merchants, I guess, leave this field empty.

[Baloo Uriza]

The SKU is for your reference only.  Wikipedia can tell you more about this.