I have really thick curly hair if I get it thined will it poof out that's what my hair dresser said that it will poof out but i don't know what she means by that that it will look like a afro or em?

Yes; it will basically become an afro. I have the same type of hair, and it's only the weight of the length that keeps it hanging vaguely downwards. I had really short hair before and as I was growing it, the fact that the short hair converted into layers as it grew meant that it was actually an afro.