It is an arrangement a parent makes for their child to live with someone who is not a close relative or guardian, for longer than 28 days.
A close relative or guardian is defined as a step-parent, grandparent, sibling, aunt or uncle, or someone who has parental responsibility.
If you care for someone else's child, who is under the age of 16 years (or 18 years if disabled) for 28 days or more, at any one time, and you are not a guardian or close relative, you are privately fostering.
It is estimated that approximately 20,000 children in the United Kingdom live away from home in private fostering arrangements. However, less than 50% of these arrangements are registered.