The customer timeline is a view of all interactions that have occurred on the customer account. This includes: payments, communications (Email/SMS/Calls), invoices, and credits raised.
Different communication statuses and the meanings
When sending the communication or looking through the customer timeline you will be able to see a history of the communications and those communications will have status.
Below are statuses for the different communication types:
Read: The email you sent has been read
Delivered: The email you sent has successfully been delivered
Delivered: The SMS you sent has successfully been delivered
Completed: A call that has been received or made is marked as completed