Let's look at what the pope said: "[B]y the authority which Christ conferred upon Peter and his Successors, in communion with the Bishops . . . I declare that direct abortion, that is, abortion willed as an end or as a means, always constitutes a grave moral disorder, since it is the deliberate killing of an innocent human being" (Evangelium Vitae 62). The Pope defines direct abortion as "abortion willed as an end or as a means." Abortion is willed as an end (that is, as a goal) if one's goal is to end the pregnancy. Abortion is willed as a means if ending the pregnancy is the instrument one uses to obtain some other goal. Abortion would be used as a means if, for example, the child was killed in order to harvest its body for medical consumption, such as organ transplants or tissue research.
An abortion would be indirect if it were used neither as an end nor as a means. If a pregnant woman has a cancerous womb that must be removed, removing it would produce an indirect abortion. The child would die after the womb is removed, but the child's death would neither be an end nor a means.
Whenever a child is actively killed, even as a means of protecting the mother's life, that constitutes direct abortion.