2 Questions; Partying advantages//Why is Rogue guild so different?

So, I'm too low a level to post 2 posts at once ene"

1. I remember partying with a friend once, and getting random gem shards while he was off getting kills; could someone explain how partying works, the advantages, lootshare systems, etc. Or link me to somewhere with all/a lot of information?

2. I just joined the Rogue's guild, but why's it so different than the rest? It's hidden away, I get that, but it also has a symbol on the minimap, the guild is instanced, etc.
Just seems so oddball compared to the other guilds .-.

Rogue was added in after the 2.0 launch, some patches later. They're a secretive bunch so they're hidden away like that.

As for those drops you were getting, mob kill drops just go to a random party member, simple as that. If you're close enough you get exp for their kills (assuming one isn't massively out levelling the mob). If you party with a mentor you get bonus exp.