FINA stands for Federation International de Natation (which is French for Swimming.) They are the international governing body of the Sport of Swimming.
When swimming at State and National levels, swimmers are required to wear FINA approved racing bathers which will carry a small white FINA tag somewhere on them.
Normal, Speedo-type bathers are acceptable. However, girls knee-length suits and boys jammers are subject to FINA rules. Basically, they must be of woven material, not go past the knee, neck or shoulders for girls and not go past the knee or navel for boys. Furthermore, they must be in one piece and not have any fastenings other than a drawstring for the jammers. Simple really.