A Facebook profile is a personal account on Facebook.
When you join Facebook, you get a Profile.
This is a place where you can connect with friends, see their posts in your news feed, post your thoughts, pictures, share videos, etc.
Your profile does not have to be strictly professional and not everything you post needs to be relevant to your niche.
That being said, it may be a good organic strategy to publish posts on your profile related to your business and add friends people who are from your niche.
Your Facebook profile is also used to create and manage business Facebook pages.