To recap from settings:

More info can be found here - But in a nut shell: When active (private) Your content is locked and only you can see it. Anyone wishing to "follow" you must be granted permission by you. If no permission is granted then they will not see your content. You will also NOT show up in site searches to non followers. 

This can be toggled on or off when ever you feel like it, but please remember: 

If you have not approved any follow requests while your account was protected, switching to public (non private) mode will automatically grant them permission to follow you, and in the event you decide to go back private, they will  beable to see your content. To prevent this happening you can use the block function to prevent them seeing your content.