Not sure how details you want those info for.

Netbackup internal processes (nb* & bp*) and workflow can be complicated and may not make sense for end user. Those are normally internal to Symantec or unless you are a partner supporting NBU.

For just a high-level overview:

Master server - media server - client connection are just like the normal backup.

Only diff is when communicating with clients (which is the Sharepoint frontend in policy), NBU looks at "Distributed Application Restore Mapping" to locate the actual Sharepoint backend (SQL) of the farm.

Therefore when a backup starts, you will see at least 3 jobs starting. One is parent job, it spawns another two, where 1 goes to Sharepoint frontend, the other goes to Sharepoint backend to backup respective components. The parent would receive status from both child jobs to determine if the whole process is good.