Hey CygnetInfo, by default all posts you post on Facebook is public. That means not only by your friends, all people (whether they logged in or not or whether they have account in Facebook or not) can see your posts by visiting your wall. If you want you can customize the visibility of the post.
1) While posting a new post in Facebook before clicking the "Share" button click the "drop-down-menu" which is in the left of "Share" button. (See link 1)
Public -> All people can see.
Friends -> Only your friends can see.
Friends of friends -> All your friends and their friends also can see.
Friends except Acquaintances -> Only your friends can see except your friends who are all in Acquaintances list.
Only Me -> Only you can see.
Custom -> You can change the visibility of the post for individual friends/list.
2) If you want to change the visibility of a post which you already posted then first go to your profile page. And Scroll down to the post which you want to change the visibility. After that click the "drop-down-menu" which you can find in between your name and your post and right side of the timing when that post was posted. (See link 2)
Link 1 for new post(s) Link 2 for old post(s) 
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