Just Curious (to mothers and the knowledgeable lol)

So i know diddly squat about pregnancy. I'm not trying to conceive and I don't think I'm pregnant or anything like that, but I would like to understand it better. There's all these acronyms and calculations and I get so lost. Like I know the basics, the anatomy, how the baby develops. I even know about implantation and implantation bleeding, but what get a me is...the calculations. Like if you have unprotected sex less than two weeks before your next due period...can you get pregnant? Will your period still come and then you just miss the next one? I know you can't get pregnant if you're not ovulating, but like if your last day of ovulation is less than two weeks before your next period and you have sex and cum finds its way inside of your body can you still get pregnant? Because I've heard it takes the fertilized egg about two weeks to implant...so would that postpone...your period?? I'm so lost. Once again I'd like to note that im not pregnant or attempting...just curious