An assortment is a specific set of items (and variants). Assortments are used to group items together in order to gain control over which customers have access to them. They also are used for assortment checks during order entry. An item can be connected to more than one assortment, and an assortment can be connected to more than one customer. Assortments are created in 'Assortment. Open' (CRS105).
Items are connected to an assortment in 'Assortment. Connect Items' (OIS072). When the item is connected, it can only be ordered by customers connected to that assortment.
Assortments are connected to customers in 'Customer. Connect Assortment' (OIS071). This allows the connected customers to order the items in the assortment.