How much do you know about Nomads? Assuming no prior knowledge:
Unlike traditional planet-based nation-states, Nomads are based on 3 ark-ships - Corregidor, Tunguska and Bakunin. Corregidor started as a cryogenic space prison, I can't remember atm where the other ships came from. What's important is that they have no permanent position, travel from system to system by attaching the ships to Circulars (huge starships that provide wormhole-based inter-system communication), and exist by the grace of O-12 (space UN), a healthy dose of bribery and blackmail, and their own sheer will to live.
The defining Nomad attribute is independence. All ships' communities started as rebels one way or another, and they don't want to go back to the ordered nanny states, especially now that there's the all-seeing eye of the AI watching everywhere. Nomads are the centre of anti-ALEPH movement, they have their own info-network (they rely mainly on their Arachne instead of the ALEPH-controlled Maya that's used in most of the Human Sphere) and consider the AI a Skynet waiting for its chance.
Each of the ships has its own different way of life:
Corregidor started as a prison and survived by hiring themselves for any kind of zero-G tech job, so they're hardened, no-nonsense and the harshest motherfuckers in space. Think oil-rig workers crossed with the Lunar colony of
The Moon is a Harsh Mistress. They still survive by being the best at space construction and EVA tech, as well as being fiercely protective of their own workers and interests (e.g. if you hire a Nomad team to overhaul your space station's systems, you might count on one of them being a disguised Intruder assigned there to evacuate the team in case the employer wanted to screw them over).
Bakunin became a refuge for all kinds of misfits, revolutionaries, freaks, religious fanatics, mutants, mad scientists, and pretty much anyone who wanted out and could pay for a module. The golden rule is "we don't care what you do inside your module as long as you behave in common zones and don't jeopardize the ship". There's probably a form of every weird ideology/religion/social movement in there. Two places you might hear about are Vaudeville (the common zones where the modules' inhabitants mingle, creating a very weird culture and a tremendous influence on Human Sphere's fashion trends) and Praxis (which is where the more serious misfits tend to end up; black laboratories where ethics is optional and less important than progress itself - and progress is defined in very strange ways. That's where weird Bakunin units (Chimeras/Pupniks) come from, it's likely that Morlocks' mutagenic drugs came from there as well.) Oh, and there's the Observance. It's an offshoot of the Catholic Church - after the pope decided to accept the AI and the resurrection process, there was a schism. What resulted is a female-dominated (Sin-Eaters do penance partly for being male) sect with a different martyr cult (st. Mary of the Knife, IIRC) with extreme rites and beliefs (return to flagellation and the like).
Tunguska doesn't have a sectorial yet so it's less-known, but it's the hub of data collection and manipulation. Basically a hacker paradise, tax heaven, data repository for hire, profably with origins in Russian Mafia.
Not gonna describe the units, you play them so you know them

Inter-faction relations: hostile to

, major powers (

) treat Nomads as a pest that's too costly to remove and can be useful once in a while,

gets some higher tech from them, friendly to

and

on the basis that minor powers have to keep together lest they be devoured by the political giants. Nomads actually provided tech and training on the cheap to

during the Commercial Wars and helped push a bill recognizing its sovereignty through O-12, to avoid a nasty precedent of stepping on the little guys.
Not sure what more I should say. Ask and I'll answer.