This is a genuinely good thing to want to learn before marriage. The basics worth knowing are the menstrual cycle, which usually runs 21 to 35 days with bleeding for 3 to 7 days, ovulation happening roughly midway through when pregnancy becomes possible, and how hormones shift mood and the body through the month.
Next Steps
For anything beyond this, like fertility planning or contraception once you're married, please consult a gynaecologist together, which is more useful than reading further online since you can ask your specific questions directly.
Health Tips
Be careful with random online sources or AI tools for specifics, since a lot of circulating information about fertility and conception is inaccurate or oversimplified.