Okay kiddo, so you know how people have different body parts, right? And you know how some people have boy body parts and some people have girl body parts? Well, the way people use those body parts to make babies and feel good and happy has changed a lot over a really long time!
When humans first started evolving a long, long time ago, they didn't think about sex and babies the way we do today. They just tried to make more babies to keep their group of people growing. This was called survival of the fittest, because the groups of people who had more babies were more likely to survive.
Over time, though, people started to realize that having sex felt good and made them happy, even if they didn't want to have babies. They started to experiment with different ways of having sex, and some groups of people decided they wanted to only have sex with certain people - like only with someone who had the same body parts as them, or only with someone they loved and trusted very much.
As humans kept evolving, they also started to think more about how they could be safe when they had sex. This meant using things like condoms to prevent diseases and unwanted babies. We also learned about how there are lots of different types of people in the world - not just boys and girls, but people who don't fit into those categories - and we should be kind and understanding to all of them.
So today, people can have sex in lots of different ways and with lots of different people, and there's no one right way to do it. But the most important thing is that everyone is safe and happy, and that we treat people with respect and kindness no matter what they look like or who they love.