Posting WIF?

Ok I keep seeing this posting WIF as alternative to using my password.
However, I can not seem to locate anything stating what it is, where to get it, or how to create it.
I have seen many posts asking this question that are several years old, but still they have no answer.
At most someone will dump all the information about the four keys.
Is the Posting WIF one of these four keys?

I tried using my posting key but it failed to be accepted.

Any help would be greatly appreciated.