wlan0, wifi0 and wmaster0

Hi All,

This may sound as  basic question to all... but iam confused.

What is the difference between all the three? when my wireless drivers
are loaded, i get 3 interfaces,

wlan0, wifi0 and wmaster0.
why are there 3 interface names...

and to use this interface ........again i create a VAP on which
interface and why??

Pl help!

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