PERLITE

[Bluey]

Thanks to everyone who replied to my first post. I received a diverse response, typifying the different areas where our orchids are grown.
So i thought i'd try this week another thing which i am finding confusing. PERLITE.
Most, but not all growers, recommend the use of it, or peanuts, or something similar. Some say it MUSTgo into the very bottom of the pot, some say the very top. Others say it should be mixed up with the medium.
Is there a right answer? Also, if its function is to retain moisture, isn't that running counter to the advice of using a free draining orchid mixture? Should we be clogging up the mixture around the roots and maybe rotting them?
Hey, I'm new. Maybe i have the kangaroo by the tail. Inform me. Please.
Bluey!