While some make everything public on purpose, many of us can be doing it accidentally. This could happen because maybe you are new to Facebook, or perhaps using a app to post to Facebook for you.
This can easily be solved in a few clicks of the mouse.
While logged into your Facebook account via your web browser:
- Click on the "lock" icon in top blue bar
- Click on the "Who Can See My Stuff" toggle
- Select "Friends" for the "Who can see my future posts?" option.
You are done.
If you have posts that are public and you want to make them all posts only your friends can see. Check out this link to the Facebook help page.