5.-Why were they built?

Cardiff Castle- The castle was built as Roman Fort.
Raglan Castle- The castle was built as the strength of the great family of Herbert.
Caerphilly Castle- The castle was buil for Uywelyn ap Gruffudd to stop ambitions south.
Chepstow Castle- It was the southermost of a chain of castles built along the English border in Welsh Marches. It was built to subdue the Welsh of Gwent.
Castle Coch- The castle was rebuilt in stone and consisted of a keep, a fortress.