How would this be put into the words of a 14 year old?

Essentially a variation on the swastika, and popular for that reason, the triskele was a symbol occasionally used by the Nazi regime, most notably as the insignia for a Waffen SS division composed of Belgian volunteers. After World War II, the "Three Sevens" version of the triskele was popularized by white supremacists in Europe and South Africa. One South African group, the AWB, used it as its flag, claiming that the three sevens symbolized supremacy over the devil. The symbol is also used as part of the logo of the international racist skinhead group, Blood & Honour.