Thank you so much for both your answers. And thank you Annie for the January scenario otherwise I would have never understood lol. God bless you both :)
Do you mean what is the difference between your "fertile window" and ovulation? (Sometimes the phrase 'fertile window' is seen on conception calculators.) A fertile window is the length of time a sperm can last in your body, which is longer than the 1-2 days your egg is good for being fertilized. If you and someone had sex on January 1, your fertile window from that sexual encounter would be 5 or 6 days long because that is how long sperm would last in your system. If you ovulated within that time, you could get pregnant (given, of course, that the sex was unprotected).
Ovulation is when one of your eggs isv released from your ovary. You can only get pregnant while you're ovulating. Fertile just means that you are able to have a child.
Hope this helps!