New user - for sale forum question "HF"?

In looking at the For Sale forum I see the following:

"HF is probably a better place to reach people for selling most stuff. We reach the same kinds of people as HF, but HF gets 7,000,000 sessions and 35,000,000 page views per month. We are about 1000 times smaller and the members here are much more selective in what they purchase."

Can someone please enlighten me as to what "HF" is?

Thank you!

 

https://www.head-fi.org/classifieds/

 

Head-fi

This would be better posted in the general advice thread, or as a profile update.

 

Thank you for the quick reply!