what does it mean in simple words? as one of many StackOverflow contributors (although very small) I don't want that my answers were wall-guarded by SO website,

what does it mean in simple words? as one of many StackOverflow contributors (although very small) I don't want that my answers were wall-guarded by SO website, they are free to use advertising revenue from traffic generated by my content to remunerate for creation and supporting the platform, but the content itself is mine, why it shouldn't be that way?