The word ‘Private’ refers to personal belonging. A private social media account provides you access to control your social interaction. Only the followers you approve can see any social media activity you perform. On social media, various social media platforms allow users to choose between a private or public account. Instagram uses this feature widely and helps people create a comfortable and secure social presence.

On Facebook, you can create groups and communities and set them as private if you want a limited and relevant number of users to interact with you. 

Example 

Search for any account you want to follow, and if it requires you to request the owner to allow you as a follower, it means the account is private and is accessed by the allowed followers only.