Can someone explain to me what are these PA badges in my Steam inventory? How to get them, what to do with them? I see that I can sell them for 0.10 euros, is that all? Or there is something more? I am not familiar with Steam games, so please...
You can trade them or sell them. Most games give trading cards one or two usually, some members of steam have really gotten into the trading cards. Basically if you don't want them just sell them for the couple cents their worth.
I sold a bunch of duplicates and made a SHOCKING 86 cents. If you're selling just make the price one cent lower than everyone else.
Not really familiar with it too, but you can gather all trading cards to make a badge. Usually you get half of the ones available (provided you don't get duplicates) by playing. To get the other half, you have either to buy the remaining ones, or trade/sell cards from other games you don't care (that's what I usually do). Or you can play the trader in Steam Marketplace (but since Steam takes a cut of 15%, that's kind of meh)
Steam has an FAQ page for the entire card system. So just look at that. http://steamcommunity.com/tradingcards/faq/