“Your body - your choice” refers to the basic human right that you’re your own master and no one else can own/control you.
It’s especially used in the discussion about whether abortion should be legal or not, where it refers to the fact that the fetus in a pregnant person is indeed part of that person, and they are allowed to do what they want with their own body (e.g. abortion).
The post mentions the opposite, “your body, our choice” which refers to the anti-abortion movement where people, often due to religious reasons, think they should have control over a pregnant person’s body, rather than the pregnant person themself.
Thanks for linking to the wiki page. Now I know what I don’t need to read since I also knew exactly what Web 3.0 was.