Here's what I figured so far: Personal Boundaries, an expression that did not exist in my maternal language when I grew up, refers to the physical and imaginary "lines" a person draws around themselves, to separate and distinguish themselves from the surrounding environment and others.
Simply, boundaries are what makes you be you and not someone else.
You have physical boundaries: your skin and your senses. Establishing clear boundaries means that you get to decide and communicate what goes in and out of your mouth, eyes, ears (what you look at, and listen to), who, when and where they touch you or do things with or to your body. Your physical boundaries extend to your property (you get to decide, and should communicate clearly, what happens with your money, car, toothbrush, bra and olive oil. Unless the olive oil belongs to the family, in which case it's a collective boundary and you guys get to defend it agains predators. Boundaries extend to your dependents as well: you get to decide where your child, dog, cat or goldfish sleeps tonight, and any other night, who walks with them (well, not the fish) and where and when. You get the gist.
There are non-physical boundaries too, which are imaginary lines drawn on your preferences, lifestyle choices, activities and conversations you engage in etc. You get to decide what to work, who to befriend, what conversations you participate in, what kind of language or treatment is acceptable for you from others, where do you draw the line in relational agreements. If I ever write the Boundaries! manual, I'll write examples in it. Should I?
As an autonomous human being you are responsible for establishing, communicating and defending your boundaries. As a people please like myself, you have to begin by figuring out who you are and what your boundaries are when you are not trying to please or appease anyone. Tough one, after growing up in an oppressive culture, and practicing being oppressed victim for so long, I am now in the midst of figuring all of this for myself. Who am I, not who I think that others think I should be.
As a social being, to live and function with one another, I found, it takes two or more autonomous humans with clear and healthy boundaries. You must know who you are before you commune with another, or things get really messy. Don't ask!
Would it be helpful to you to give you specific examples of learned boundaries, from my own experience?