Factions
Factions in FOnline: Aftertimes are communities. They are divided in two groups, NPC-driven and player-driven. Your character can only be in one faction at a time, either a player one or a NPC one.
Player Factions
Player-driven factions are gangs. They have a base and a faction name, and they use it to seize Town Control of a town or simply to share the same hideout.
The player-driven factions list is on the Player-Driven Factions article.
NPC Factions
NPC factions are official, like the Vault City faction or the Enclave faction. Joining one of them is useful, because you will be able to meet instructors for professions, and to make some private quests. But you won't be able to be in a player-driven faction until you resign from your current one. You can join and leave a faction freely, but (unlike player-driven factions) it will affect your reputation, so be careful.
See the NPC-Driven Factions category for more details.
NPC Factions | Player Factions | Bases | Town Control | Reputation |