If you
honestly do not understand, then a brief synopsis:
Libertarians are not anarchists - they believe that the government exists to defend our rights. Including our rights to life, liberty, and property. The
real question in the abortion topic, then, is not whether or not it is right for government to constrain a womans (or anyones') choice - but
when it is appropriate to do so. I would constrain, for example, a woman's choice to steal from me, or a mans' choice to rape my wife, and still be completely within the boundaries of libertarian principles because I am then using government to protect my right to property, my wifes' right to ownership of her own body, etc. So, if an unborn child is not a child, then the libertarian must (if he or she is to be true to their principles) accept that government does not have any right to interfere with the womans' freedom of action. But if an unborn child
is a child, then the libertarian must require that government defend its' right to life, and constrain the choices of those who would abuse those rights.
Ron and
Rand Paul, for example, are two notable Libertarian leaders who hold this position.
As for those who try to split the baby, and say that they are personally against abortion, but not against it's banning - that is (imo) an untenable position. It's like saying (from the perspective that an unborn child is a child) that you are personally against slavery or child-rape, but don't think that the government should have a hand in reducing that kind of behavior.