hello everyone

I have been searching the Internet and the forum for quite some time now but I haven't been able to have clear answers , hopefully this is the right sub forum/if not I apologize 

I have had interest in the sheriff sale tax collection and tax delinquent sales in Philadelphia,pa. I have been to some auctions to watch and I have also been watching properties and researching them .

I am confused though about these specific sales, are all liens forgiven ? I spoke with people I know that are experienced with these types of auctions and one had said at a tax auction all liens are wiped clean and all you pay is the final bidding amount.

I am reading that some people say that isn't true "taxes are almost never waived"

Or things like --

"At sheriff’s sale, the entity that holds the liens sets the listing price, or bid minimum. In a mortgage sale, the mortgage company sets the bid minimum. In a municipal (tax or L&I) lien sale, the City or its collection agencies sets the bid minimum. The bid minimum is typically equal to the lien amount. When the property is sold, the sale proceeds are applied to the remaining municipal liens. Applying the proceeds clears all liens from the property, even if the proceeds do not cover the liens entirely. This way, the new owner has clear title to the property. "

All of the auctions I am talking about specifically are either Linebarger tax collection/delinquent sherif sale auctions. 

So what is it, are the liens thrown away? If not what kind of liens can still be attached? 

I know I can do searches through city hall here to check the liens on the homes but the site is down for maintenance now and it's the weekend so I can't go to city hall, but even when I do search these things i still won't know!

What exactly should I be looking for to see how much I possibly need to pay if everything isn't wiped clean?

I am still a beginner and i am sure I'll have more questions but any help with this I would appreciate a lot. Thanks!