MongoDB Auditing vs. Profling
Profiling collects information about "what, when and how information was queried + how much time it took + what was DB engines solution"

Auditing tell "who did what and when" (who red/accessed f.ex. user information)

Logging is higher level information telling what DB did and when. When client makes/closes connection, new index is created, data is replicated, engine errors happened...

So, if law says that "we need to know who (as a person) accessed specific information", you do auditing.

To find out "which queries are slowest/take time and WHY" you use profiling.

To know what's happening and what are errors on database level, you use log files.