If a club, school, company, or group is affiliated, it is a member of a larger organisation, or is closely tied to it. A small clinic may be affiliated with a big hospital. A local club may be affiliated with a national body. The smaller one is not the same as the larger one; it belongs, partners, or sits under that bigger name. People are also described as affiliated with a university or a party, meaning they have an official link, not just a liking. It is a calm, official word — more at home on websites and in reports than in chat. Though actually, speakers sometimes stretch it to mean vaguely connected. The tidy use is a real, named link you could point to.