Plan B is NOT the so-called “abortion pill”. If a woman is already pregnant, Plan B does NOTHING. (Though women who know they are pregnant should not take the pill/s.)
Plan B is a higher dose of (synthetic) progestogen a hormone found in many birth control pills women take daily. Progestogen prevents ovulation from occurring in the days following its use and MAY prevent fertilization and implantation. Just like the regular hormonal birth control pill.
Plan B costs $40-$50 per box (though this price may change over the coming months.) It also has stronger side-effects than the regular hormonal birth control pill, including nausea. It only prevents ovulation from occurring in a short window of days AFTER it is taken—if a woman was already ovulating, she may well get pregnant following the use of Plan B. Following that short window, a woman may ovulate; if she has sex in this time frame, she may get pregnant. For these reasons, it is an ineffective means of regular, monthly birth control.
“Plan B” is the brand name of levonorgestrel (a particular synthetic progestogen.) There are generics of this drug. However, the generics have NOT been approved for over-the-counter sales.
Plan B is intended to be an EMERGENCY, BACK-UP contraceptive, when other means of contraception fail.
If you have concerns about a woman in your life using Plan B ineffectively, please explain this to her. If you are concerned that she will not be able to take two pills exactly 12 hours apart, please stress to her how important this is and show her how to set an alarm on her phone, in case she EVER needs to.