Why does websites say plan b works by causing delay on ovulation and other says it prevents ovulation im confused does it delay?

It can do both: Plan B is a high dose of hormones given all at once. The idea is to disrupt the normal hormonal balance to delay or to prevent ovulation. When used correctly it decreases the risk of pregnancy by about 70%. One can not determine in any one individual whether or not it will delay ovulation, prevent ovulation or not work during any one menstrual cycle. Use birth control to avoid this issue