Abortion is the medical practice of terminating a pregnancy. Abortion is allowed by law in many Western nations (including nominally Christian nations such as the UK).
People who believe that abortion is acceptable are described as "Pro-Choice" - choice in this case referring to the right to choose whether or not to have an abortion. Those who believe that abortion is unacceptable are described as "Pro-Life." Religious belief and a Pro-Life attitude commonly go together, but one by no means implies the other. The terms "pro-choice" and "pro-life" are examples of political framing.
In modern times abortion is a surgical procedure, but the ancients had their forms of abortion as well. In ancient Greece, for example, the practice was to have the pregnant woman drink a poison that would force her to have a miscarriage.