Infertility means not being able to make a baby. Your doctor usually won't say you have infertility until you've tried for at least a year to get pregnant.
It can be caused by problems inside the woman's body or the man's body. But sometimes no cause can be found.
Being told that you have this problem doesn't necessarily mean that you will never get pregnant. Often, couples eventually conceive without help. But medical treatments do help many couples.