The notification triggers for the product can be added to control some notifications and approvals you want to customize. These notifications automatically stop any process flow to wait for an approval. 
The notifications are used to support any follow-up of tasks that are outside the normal process flow, such as document control, QA related issues, or various approvals 

The list of types and object statuses is as follows (with the status of the document item in parentheses):

Shipping Advice (CSA)
Pending adding to picking queue (ST=1)
Pending picking (ST=2)
Pending shipping (ST=3)

Goods Reception (SSA)
Pending Label Print (ST=1)
Pending Registration (ST=2)
Pending Invoice (ST=3)

You will get different choices based on the object type and each choice will be linked to approval application (APC) and an approval rule or just an information message.

For example:

More information on Notification triggers can be found here: Notification triggers