From the introduction:
Living Forgotten Realms characters have the opportunity to meet any number of groups during their adventures, making new allies and fierce foes. It is possible that your character may wish to become a member of one or more of these groups. Some organizations offer no prestige other than your ability to claim membership, while others have significant requirements and offer actual mechanical benefits to your PC. These groups help define your character and are often closely involved in the stories that help make up the adventures of the LFR campaign. These are meta-organizations (also referred to as meta-orgs) and this guide details those meta-orgs that are currently available in LFR for your PCs to join, along with any requirements or benefits you might gain for being a member.