facebook privacy question?

[MЇŚςΗλ]

i want to join some groups and post things on said groups walls.
but facebook has no privacy and EVERYONE sees what im doing, its just my mom and grandma and aunts have a facebook too.

when i go to my page and click the x to hide what i just did does that hide it from everyone, or how can i make personal what i do.




or does it tell people when i write on a groups wall