An emblem is any recognizable symbol denoting membership in a faction or organization. This could be the sigil of a noble House, a company brand, or a logo for a faction or other organization.
They are considered highly important in the post-virus world, as belonging to a faction is a necessary element of survival. Emblems are everything to the common populace, and factions expend considerable effort in creating and maintain their emblem's reputation. Those without emblems are considered worthless. These are called slicks. One notable exception is the freebadge, or freelancer. These are usually lone mercenaries or bounty hunters, and because of their skills they are afforded respect that is typically denied for others without emblems.
Emblems can appear anywhere, though most factions will usually all wear their emblems the same within an organization. Most emblems are worn on the sleeve or chest, though some are seen on cloaks or armor.