Applying Row Level Security

Summary

Does anyone know how row level security really works?

Content

I am researching row level security. I have read the config guide for 15A and the Oracle documentation Doc ID 1909934.1, but neither of these resources actually says specifically how this works.  It tells you how to configure it, but not any sort of reasoning to, or not to, use it.

Any insight into understanding how it works and functions would be appreciated.