There are 4 major guilds in the Empire of Olera, where anyone with a title can petition for a team to perform tasks ranging from bodyguarding to cave extermination. The guilds are mostly there for story flavor purposes, but there are bonuses to each one listed at the end of their description.
Craftsmen Guild, where traders, smiths, and alchemists work to further the economy of their cities and line their own pockets with gold. (+5 to Diplomacy when haggling)
Protector's Guild, where fighters, paladins, and others can join the military or police force and work to keep Olera safe from dangers near and far. (+5 Intimidation)
The Magus Guild, where clerics, sorcerers, and wizards meet to discuss the merits of the various schools and styles of magic, and how they can be applied to better the lives of everyday citizens. (+5 Knowledge (Arcana) or Spellcraft)
The Explorer's Guild, where bards and rangers work to explore the caverns and tombs left behind from the Reign of Damos. (+5 Survival or +5 Knowledge(Dungeoneering))
There is also a Thieves' Guild, but nobody knows much about it, other than its members, who usually blend in with other guilds to maintain their covers (especially the Explorer's Guild) (+5 Sleight of Hand or Disguise).
The guild leaders all meet with the King monthly to discuss the state of things in their realm of control.
If you have any other questions, feel free to ask.