Fertility and ovulation


So I know it will sound completely stupid. I was so ignorant when I got pregnant at 21 and had my daughter and now 34 almost. I have been learning so much since we are now trying to have a baby again BUT how is it you can have high fertility days prior to ovulation? Ovulation is when the egg gets released. So wouldn’t it be more convenient to do the BD the day before or after. Nothing other than that. I’m a bit confused. Yes I know I should know all this. But honestly I just went with life unless something ever was wrong or came up. Then I looked for answers.