Like Pro-life, Pro-choice is a term commonly used by activists in the abortion issue. Those who call themselves "pro-choice" favor reduced or eliminated federal government restrictions on abortion. The term was designed to make people think there are only two sides to the issue of abortion.
The term suggests that opponents are "anti-choice" (and indeed some who call themselves pro-choice label their opponents thus), and also suggest that the most important aspect of the abortion issue is a pregnant woman's right to choose the outcome of her pregnancy.
Although the term does not mention abortion, in practice this term is limited to the abortion issue. Not all those who call themselves "pro-choice" favor "choice" in all other public issues. In particular, relatively few are libertarians across the board. Some who would be Pro-choice prefer that abortion be legal on the State instead of Federal level, and thus are not Pro-choice.
(This entry is a close counterpart of the Pro-life entry.)