Do you mean a family report?
If so, a family report is an assessment of the family dynamic. Essentially, it is used to identify any opinions a child might have about their living arrangements, assess how healthy or established a child's attachment to each parent is, uncover any issues around alienation or similar, and basically provide an outline to the court of any problems that might exist, and any recommendations as to how those problems could be addressed by orders.
Family reports are carried out by experts in the field - usually a child psychologist or a social worker - in association with the kids, the parents and other people who might play a particularly significant part in the kids' lives, such as grandparents or step-parents. All such parties will be interviewed and observed interacting with the child.
The primary function of a family report in terms of court proceedings is to provide the court with an expert opinion about what is or isn't in the child's best interests.
Anyway, I hope this helps.