Popfags are people that enjoy music along the lines of Pop, R&B, Hip-hop or any genres associated with that shit. A popfag is also someone that dresses or will to look as much like either Justin Beiber, or Jason Derulo as they can and just end up looking like faggots
Metalhead 1: Omg check out those faggots
Metalhead 2: They aren't just faggots, they are popfags
A "Live Loser" is generally an 8-16yo who are a pain in the ass all over the internet, especially Xbox live, where they continue to think they rule everything, everywhere. Also known as Trollers, these idiots continue on their tyrannous so called "Reign of the Internet" posting and trying to act cool on various sites all over the internet. They are also people that have absolutely no hope of ever getting laid.
Normal person: "I had such a fun day outside with my real friends and girlriend"
Live Loser: "Well I had lots of fun having cyber sex with my girlfriend I met on Xbox Live and then I completely pwned some n00bs on Halo"