Boyfriend's arm around waist meaning?

Ive been going out with him for nearly a month now, and whenever we walk, sit or stand anywhere, he always keeps his arm around my waist. I have no problem with it, in fact I love it, but I just wanna know exactly what it means. Also does the lower he put it mean something too? The other day his arm was resting pretty much just at the top of my butt.
Boyfriend's arm around waist meaning?
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