Article enrichment
The articles in transactions don't contain any of the useful product data or metadata. This is to save space in the transmission and importing of transactions, but also to allow flexibility in adding product data later, a process known as "enrichment".
Important
Enrichment is linking the articles on a transaction with their product data.
An article's SKU code is the key to enrichment. Since an SKU exists both for the article on the transaction and in the article register, this allows the two to be connected.
The SKU is mapped to "ArticleNr" in Engage. Note that a line-item row in Engage always refers to the most detailed version of a specific article.
You can read more about this in the introduction to transactions.