I'm sorry the concept of boundaries being used to define specific areas are beyond you. Not sure how else I can help. If you look at the boundaries of any modern map of the geography of the earth, nothing is in straight lines. The borders of countries are very complicated shapes, yet you pretty much know if you are in a country or not. Cities are the same way, yet you probably know when you leave your city. Breaking into smaller neighborhoods it gets even more confusing, but yet again, you probably know when you're in your neighborhood or you're in the one next door. Knowing those boundaries comes from experience traveling around the areas. It'll happen the same way if you actually study astronomy versus just being obtuse about a subject on the internet.