When you begin building a Facebook Ad, you are defaulted to building a core audience when choosing you ad targeting.
Anything a person puts on Facebook is calculated into their data for you to market to.
Demographics, locations, interests, behaviours and connections make up the data for a core audience.
Demographic targeting draws from information that people share publicly on Facebook about their education, political views, family/relationship status, life events, career, and more.
Location targeting allows marketers to target ads by postal code, city, region, or country — or worldwide — and to deliver ads based on where people are, whether they live in a location, are new arrivals, or just visiting.
Interest targeting focuses on consumer and lifestyle categories such as fitness, fashion, or hobbies.
Connections targeting is based on audience engagement with your Facebook Page, Facebook Events, or app.
If you can’t figure out why this is important, then I suggest you find a new career.